A   MANUAL 


OF 


ENGINEERING    DRAWING 


FOR 


STUDENTS  AND  DKAFTSMEN; 


BY 


THOMAS  E.  FRENCH,  M.  E. 

PROFESSOR   OP   ENGINEERING   DRAWING,   THE   OHIO   STATE   UNIVERSITY 


NEW  YORK 

McGRAW-HILL   BOOK   COMPANY 

239  WEST  39TH  STREET,  NEW  YORK 

1911 


COPYRIGHT,  1911 

BY  THE 
MCGRAW-HILL  BOOK  COMPANY 


Printed  and  Electrotyped 

by  The  Maple  Press 

York,  Pa. 


PEEFACE 


There  is  a  wide  diversity  of  method  in  the  teaching  of  engineer- 
ing drawing,  and  perhaps  less  uniformity  in  the  courses  in  differ- 
ent schools  than  would  be  found  in  most  subjects  taught  in 
technical  schools  and  colleges.  In  some  well-known  instances 
the  attempt  is  made  to  teach  the  subject  by  giving  a  series  of 
plates  to  be  copied  by  the  student.  Some  give  all  the  time  to 
laboratory  work,  others  depend  principally  upon  recitations  and 
home  work.  Some  begin  immediately  on  the  theory  of  descrip- 
tive geometry,  working  in  all  the  angles,  others  discard  theory 
and  commence  with  a  course  in  machine  detailing.  Some 
advocate  the  extensive  use  of  models,  some  condemn  their  use 
entirely. 

Different  courses  have  been  designed  for  different  purposes, 
and  criticism  is  not  intended,  but  it  would  seem  that  better  unity 
of  method  might  result  if  there  were  a  better  recognition  of  the 
conception  that  drawing  is  a  real  language,  to  be  studied  and 
taught  in  the  same  way  as  any  other  language.  With  this 
conception  it  may  be  seen  that  except  for  the  practice  in  the 
handling  and  use  of  instruments,  and  for  showing  certain  stand- 
ards of  execution,  copying  drawings  does  little  more  in  the  study 
as  an  art  of  expression  of  thought  than  copying  paragraphs  from 
a  German  book  would  do  in  beginning  the  study  of  the  German 
language. 

And  it  would  appear  equally  true  that  good  pedagogy  would 
not  advise  taking  up  composition  in  a  new  language  before  the 
simple  structure  of  the  sentence  is  understood  and  appreciated; 
that  is,  " working  drawings"  would  not  be  considered  until  after 
the  theory  of  projection  has  been  explained. 

After  a  knowledge  of  the  technic  of  expression,  the  "pen- 
manship and  orthography/'  the  whole  energy  should  be  directed 
toward  training  in  constructive  imagination,  the  perceptive 
ability  which  enables  one  to  think  in  three  dimensions,  to  visual- 

v 

222476 


vi  PREFACE 

ize  quickly  and  accurately,  to  build  up  a  clear  mental  image,  a 
requirement  absolutely  necessary  for  the  designer  who  is  to 
represent  his  thoughts  on  paper.  That  this  may  be  accomplished 
more  readily  by  taking  up  solids  before  points  and  lines  has  been 
demonstrated  beyond  dispute. 

It  is  then  upon  this  plan,  regarding  drawing  as  a  language,  the 
universal  graphical  language  of  the  industrial  world,  with  its 
varied  forms  of  expression,  its  grammar  and  its  style,  that  this 
book  has  been  built.  It  is  not  a  "course  in  drawing,"  but  a 
text-book,  with  exercises  and  problems  in  some  variety  from 
which  selections  may  be  made. 

Machine  parts  furnish  the  best  illustrations  of  principles,  and 
have  been  used  freely,  but  the  book  is  intended  for  all  engineering 
students.  Chapters  on  architectural  drawing  and  map  drawing 
have  been  added,  as  in  the  interrelation  of  the  professions  every 
engineer  should  be  able  to  read  and  work  from  such  drawings. 

In  teaching  the  subject,  part  of  the  time,  at  least  one  hour  per 
week,  may  profitably  be  scheduled  for  class  lectures,  recitations, 
and  blackboard  work,  at  which  time  there  may  be  distributed 
"study  sheets"  or  home  plates,  of  problems  on  the  assigned 
lesson,  to  be  drawn  in  pencil  and  returned  at  the  next  correspond- 
ing period.  In  the  drawing-room  period,  specifications  for  plates, 
to  be  approved  in  pencil  and  some  finished  by  inking  or  tracing, 
should  be  assigned,  all  to  be  done  under  the  careful  supervision 
of  the  instructor. 

The  judicious  use  of  models  is  of  great  aid,  both  in  technical 
sketching  and,  particularly,  in  drawing  to  scale,  in  aiding  the 
student  to  feel  the  sense  of  proportion  between  the  drawing  and 
the  structure,  so  that  in  reading  a  drawing  he  may  have  the 
ability  to  visualize  not  only  the  shape,  but  the  size  of  the  object 
represented. 

In  beginning  drawing  it  is  not  advisable  to  use  large  plates. 
One  set  of  commercial  drafting-room  sizes  is  based  on  the  division 
of  a  36"x48"  sheet  into  24"x36",  18"x24",  12"xl8"  and  9"xl2". 
The  size  12"xl8"  is  sufficiently  large  for  first  year  work,  while 
9"xl2"  is  not  too  small  for  earlier  plates. 

Grateful  acknowledgement  is  made  of  the  assistance  of  Messrs. 
Robert  Meiklejohn,  O.  E.  Williams,  A.  C.  Harper,  Cree  Sheets, 
F.  W.  Ives,  W.  D.  Turnbull,  and  W.  J.  Norris  of  the  staff  of  the 
Department  of  Engineering  Drawing,  Ohio  State  University,  not 


PREFACE  vii 

only  in  the  preparation  of  the  drawings,  but  in  advice  and 
suggestion  on  the  text.  Other  members  of  the  faculty  of  this 
University  have  aided  by  helpful  criticism. 

The  aim  has  been  to  conform  to  modern  engineering  practice, 
and  it  is  hoped  that  the  practical  consideration  of  the  draftsman's 
needs  will  give  the  book  permanent  value  as  a  reference  book  in 
the  student's  library. 

The  author  will  be  glad  to  co-operate  with  teachers  using  it  as 
a  text-book. 

COLUMBUS,  OHIO. 
May  6,  1911. 


CONTENTS 


PAGE 

PREFACE v 

CHAPTER  I. — INTRODUCTORY 1 

Engineering  drawing  as  a  language — Its  division  into  mechanical 
drawing  and  technical  sketching — Requirements  in  its  study.  - 

CHAPTER  II. — THE  SELECTION  OF  INSTRUMENTS 4 

Quality — List  of  instruments  and  materials  for  line  drawing — The 
pivot  joint — Points  to  observe  in  selecting  instruments — Com- 
passes—  Dividers  —  Ruling  pens — Bow  instruments — Drawing 
boards — T-squares  —  Triangles  —  Scales — Inks — Pens — Curves — 
Drawing  papers — etc.  Description  of  special  instruments  and 
devices — Railroad  pen — Curve  pen — Lettering  pens — Proportional 
dividers — Beam  compass — Drop  pen — Protractor — Section  liners 
— Drafting  machines — Vertical  drawing  boards — Other  instru- 
ments and  appliances. 

CHAPTER  III.— THE  USE  OF  INSTRUMENTS 23 

Good  form  in  drawing — Preparation  for  drawing — The  pencil — The 
T-square — Laying  out  the  drawing — Use  of  dividers — To  divide  a 
line  by  trial — Use  of  the  triangles — Use  of  the  compasses — Use 
of  the  scale — Inking — Faulty  lines — The  alphabet  of  lines — Use  of 
the  French  curve — Exercises — A  page  of  cautions. 

CHAPTER  IV. — APPLIED  GEOMETRY 47 

Applications  of  the  principles  of  geometry  in  mechanical  drawing — 
To  divide  a  line  into  any  number  of  parts — To  transfer  a  given 
polygon  to  a  new  base — To  inscribe  a  regular  octagon  in  a  square — 
To  draw  a  circular  arc  through  three  points — To  draw  an  arc  tan- 
gent to  two  lines — To  draw  an  ogee  curve — To  rectify  an  arc — The 
conic  sections — Methods  of  drawing  the  ellipse — Approximate  ellip- 
ses— The  parabola — The  rectangular  hyperbola — The  cycloid — 
The  epicycloid — The  hypocycloid — Involutes — The  spiral  of 
Archimedes. 

CHAPTER  V.— LETTERING      58 

Importance — Should  be  done  freehand — Pens  for  lettering — 
Single-stroke  vertical  caps — Single-stroke  inclined  caps — The 
Reinhardt  letter — Spacing  and  composition — Titles. 

ix 


x  CONTENTS 

CHAPTER  VI. — ORTHOGRAPHIC  PROJECTION 65 

Definition — The  planes  of  projection — Principles — Writing  the  lan- 
guage and  reading  the  language — Auxiliary  views — Sectional  views 
— Section  lining — Revolution — The  true  length  of  a  line — Shade 
lines — Problems,  in  seven  groups. 

CHAPTER  VII.^ — DEVELOPED  SURFACES  AND  INTERSECTIONS  .  .  .  100 
Classification  of  surfaces,  ruled  surfaces,  double  curved  surfaces — 
Developments — Practical  considerations — To  develop  the  hexag- 
onal prism — The  cylinder — The  hexagonal  pyramid — The  rectan- 
gular pyramid — The  truncated  cone — Double  curved  surfaces — 
Triangulation — Development  of  the  oblique  cone — Transition 
pieces — The  intersection  of  surfaces — Two  cylinders — Cylinder 
and  cone — Cutting  spheres — Two  cones — Problems,  in  ten  groups. 

CHAPTER  VIII. — PICTORIAL  REPRESENTATION 122 

Use  of  conventional  picture  methods,  their  advantages,  disad- 
vantages, and  limitations — Isometric  drawing — The  isometric 
section — Oblique  projection — Rules  for  placing  the  object — The 
offset  method — Cabinet  drawing — The  principle  of  axonometric 
projection — Dimetric  system — Clinographic  projection  and  its  use 
in  crystallography — Problems — Reading  exercises,  orthographic 
sketches  to  be  translated  into  pictorial  sketches. 

CHAPTER  IX.— WORKING  DRAWINGS 145 

Definitions — Classes  of  working  drawings — "Style"  in  drawing — 
Order  of  penciling — Order  of  inking — Dimensioning,  General 
rules  for  dimensioning — Finish  mark — Notes  and  specifications — 
Bill  of  material — Title — Contents  of  title — Requirements  in  com- 
mercial drafting — Fastenings — Helix — Screw  threads — Forms  of 
threads — Conventional  threads — Bolts  and  nuts — Lock  nuts — 
Cap  screws — Studs — Set  screws — Machine  screws,  etc. — Pipe 
threads  and  fittings — Gears — Method  of  representation — Con- 
ventional symbols  and  their  use — Commercial  sizes — Checking — 
Structural  drawing — Rivets,  Examples  of  structural  drawing, 
Differences  in  practice — Problems. 

CHAPTER  X. — TECHNICAL  SKETCHING 201 

Its  necessity  to  the  engineer — Sketching  in  orthographic  pro- 
jection— Dimensioning — Cross-section  paper — Sketching  by  pic- 
torial methods,  Axonometric,  Oblique,  Perspective — Principles  of 
perspective — Exercises. 

CHAPTER  XI... THE  ELEMENTS  OF  ARCHITECTURAL  DRAWING  .  .  214 
Characteristics  of  architectural  drawing — Kinds  of  drawings — 
Display  and  competitive  drawings — Rendering — Poohe*  and 
Mosaic — Preliminary  sketching — Use  of  tracing  paper — Working 
drawings — Plans — Elevations — Sections — Details — Dimensioning 
— Lettering — Titles. 


CONTENTS  xi 

CHAPTER  XII. — MAP  AND  TOPOGRAPHICAL  DRAWING 229 

Classification  of  Maps — Plats,  A  farm  survey,  Plats  of  subdivisions, 
City  plats — Topographical  drawing,  Contours,  Hill  shading,  Water 
lining — Topographic  symbols,  Culture,'  Relief,  Water  features, 
Vegetation,  Common  faults — Lettering — Government  Maps — 
Profiles. 

CHAPTER  XIII. — DUPLICATION,  AND  DRAWING  FOR  REPRODUCTION.   248 
Tracing — Tracing  cloth — Blue  printing,  Methods,  Formulae — Van 
Dyke    prints — Transparentizing — Various    suggestions — Prepara- 
tion of  drawings  for  reproduction — Zinc  etching — Half  tones — 
Retouching — The  wax  process — Lithography. 

CHAPTER  XIV. — NOTES  ON  COMMERCIAL  PRACTICE 257 

Suggestions  and  miscellaneous  information — To  sharpen  a  pen — 
To  make  a  lettering  pen — Line  shading,  use,  and  methods — Patent 
office  drawings,  rules,  and  suggestions — Stretching  paper  and 
tinting — Mounting  tracing  paper — Mounting  on  cloth — Methods  of 
copying  drawings — Pricking — Transfer  by  rubbing — A  transpar- 
ent drawing  board — The  pantograph — Proportional  squares — 
About  tracings — Preserving  drawings — Filing  drawings — Misel- 
laneous  hints. 

CHAPTER  XV. — BIBLIOGRAPHY  OF  ALLIED  SUBJECTS 274 

A  short  classified  list  of  books  on  allied  subjects,  Architectural 
drawing — Descriptive  geometry — Gears  and  gearing — Handbooks 
— Lettering — Machine  drawing  and  design — Perspective — Render- 
ing— Shades  and  shadows — Sheet  metal — Stereotomy — Structural 
drawing  —  Surveying — Technic  and  standards — Topographical 
drawing — Miscellaneous. 

INDEX.  281 


ENGINEERING  DRAWING 


ENGINEERING  DRAWING 


CHAPTER  I. 
INTRODUCTORY. 

By  the  term  Engineering  Drawing  is  meant  drawing  as  used 
in  the  industrial  world  by  engineers  and  designers,  as  the  lan- 
guage in  which  is  expressed  and  recorded  the  ideas  and  informa- 
tion necessary  for  the  building  of  machines  and  structures;  as 
distinguished  from  drawing  as  a  fine  art,  as  practised  by  artists 
in  pictorial  representation. 

The  artist  strives  to  produce,  either  from  the  model  or  land- 
scape before  him,  or  through  his  creative  imagination,  a  picture 
which  will  impart  to  the  observer  something  as  nearly  as  may  be 
of  the  same  mental  impression  as  that  produced  by  the  object 
itself,  or  as  that  in  the  artist's  mind.  As  there  are  no  lines  in 
nature,  if  he  is  limited  in  his  medium  to  lines  instead  of  color 
and  light  and  shade,  he  is  able  only  to  suggest  his  meaning,  and 
must  depend  upon  the  observer's  imagination  to  supply  the  lack. 

The  engineering  draftsman  has  a  greater  task.  Limited  to 
outline  alone,  he  may  not  simply  suggest  his  meaning,  but  must 
give  exact  and  positive  information  regarding  every  detail  of  the 
machine  or  structure  existing  in  his  imagination.  Thus  drawing 
to  him  is  more  than  pictorial  representation;  it  is  a  complete 
graphical  language,  by  whose  aid  he  may  describe  minutely  every 
operation  necessary,  and  may  keep  a  complete  record  of  the  work 
for  duplication  or  repairs. 

In  the  artist's  case  the  result  can  be  understood,  in  greater  or 
less  degree,  by  any  one.  The  draftsman's  result  does  not  show 
the  object  as  it  would  appear  to  the  eye  when  finished,  conse- 
quently his  drawing  can  be  read  and  understood  only  by  one 
trained  in  the  language. 

1 


2  ENGINEERING  DRAWING 

Thus  as  the  foundation  upon  which  all  designing  is  based, 
engineering  drawing  becomes,  with  perhaps  the  exception  of 
mathematics,  the  most  important  single  branch  of  study  in  a 
technical  school. 

When  this  language  is  written  exactly  and  accurately,  it  is 
done  with  the  aid  of  mathematical  instruments,  and  is  called 
mechanical  drawing.*  When  done  with  the  unaided  hand, 
without  the  assistance  of  instruments  or  appliances,  it  is  known 
as  freehand  drawing,  or  technical  sketching.  Training  in  both 
these  methods  is  necessary  for  the  engineer,  the  first  to  develop 
accuracy  of  measurement  and  manual  dexterity,  the  second 
to  train  in  comprehensive  observation,  and  to  give  control  and 
mastery  of  form  and  proportion. 

Our  object  then  is  to  study  this  language  so  that  we  may  write 
it,  express  ourselves  clearly  to  one  familiar  with  it,  and  may 
read  it  readily  when  written  by  another.  To  do  this  we  must 
know  the  alphabet,  the  grammar  and  the  composition,  and  be 
familiar  with  the  idioms,  the  accepted  conventions  and  the 
abbreviations. 

This  new  language  is  entirely  a  graphical  or  written  one.  It 
cannot  be  read  aloud,  but  is  interpreted  by  forming  a  mental 
picture  of  the  subject  represented;  and  the  student's  success  in 
it  will  be  indicated  not  alone  by  his  skill  in  execution,  but  by 
his  ability  to  interpret  his  impressions,  to  visualize  clearly  in 
space. 

It  is  not  a  language  to  be  learned  only  by  a  comparatively 
few  draftsmen,  who  will  be  professional  writers  of  it,  but  should 
be  understood  by  all  connected  with  or  interested  in  technical 
industries,  and  the  training  its  study  gives  in  quick,  accurate 
observation,  and  the  power  of  reading  description  from  lines,  is 
of  a  value  quite  unappreciated  by  those  not  familiar  with  it. 

In  this  study  we  must  first  of  all  become  familiar  with  the 
technic  of  expression,  and  as  instruments  are  used  for  accurate 
work,  the  first  requirement  is  the  ability  to  use  these  instruments 
correctly.  With  continued  practice  will  come  a  facility  in  their 
use  which  will  free  the  mind  from  any  thought  of  the  means  of 
expression. 

*  The  term  "Mechanical  Drawing"  is  often  applied  to  all  constructive 
graphics,  and,  although  an  unfortunate  misnomer,  has  the  sanction  of  long 
usage. 


INTRODUCTORY  3 

A  knowledge  of  geometry  is  desirable  as  there  will  be  frequent 
applications  of  geometrical  principles. 

We  recommend  therefore,  as  preliminary,  the  drawing  of  one 
or  two  practice  plates,  and  a  few  of  the  geometrical  figures  of 
Chapter  IV  which  are  often  referred  to,  before  the  mind  is 
occupied  with  the  real  principles  or  "  grammar  "  of  the  language. 


CHAPTER  II. 

THE  SELECTION  OF  INSTRUMENTS. 

In  the  selection  of  instruments  and  material  for  drawing  the 
only  general  advice  that  can  be  given  is  to  secure  the  best  that 
can  be  afforded.  For  one  who  expects  to  do  work  of  professional 
grade  it  is  a  great  mistake  to  buy  inferior  instruments.  Some- 
times a  beginner  is  tempted  by  the  suggestion  to  get  cheap 
instruments  for  learning,  with  the  expectation  of  getting  better 
ones  later.  With  reasonable  care  a  set  of  good  instruments  will 
last  a  lifetime,  while  poor  ones  will  be  an  annoyance  from  the 
start,  and  will  be  worthless  after  short  usage.  As  good  and  poor 
instruments  look  so  much  alike  that  an  amateur  is  unable  to 
distinguish  them  it  is  well  to  have  the  advice  of  a  competent 
judge,  or  to  buy  only  from  a  trustworthy  and  experienced  dealer. 

This  chapter  will  be  devoted  to  a  short  description  of  the  instru- 
ments usually  necessary  for  drawing,  and  mention  of  some  not 
in  every-day  use,  but  which  are  of  convenience  for  special  work. 
In  this  connection,  valuable  suggestions  may  be  found  in  the 
catalogues  of  the  large  instrument  houses,  notably  Theo.  Alteneder 
&  Sons,  Philadelphia;  the  Keuffel  &  Esser  Co.,  New  York,  and 
the  Eugene  Dietzgen  Co.,  Chicago.  With  the  exception  of  the 
Alteneder  instruments,  all  drawing  instruments  are  made  abroad, 
principally  in  Germany.  Scales,  T-squares,  surveying  instru- 
ments, etc.,  are,  however,  made  in  this  country. 

The  following  list  includes  the  necessary  instruments  and 
materials  for  ordinary  line  drawing.  The  items  are  numbered 
for  convenience  in  reference  and  assignment. 

List  of  Instruments  and  Materials. 

1.  Set  of, drawing  instruments,  in  case  or  chamois  roll,  including  at 
least:   5   1/2  in.  compass,  with  fixed  needle-point  leg,  pencil, 
pen,  and  lengthening  bar. 
5-in.  hairspring  dividers. 
Two  ruling  pens. 
Three  bow  instruments. 
Box  of  hard  leads. 

4 


THE  SELECTION  OF  INSTRUMENTS  5 

y2.  Drawing  board. 

'  3.  T-square. 

/4.  45°  and  30°-60°  triangles. 

*r  5.  12-in.  architects'  scale  (two  flat  or  one  triangular). 

x  6.  One  doz.  thumb  tacks. 

*    7.  One  6  H  and  one  2  H  drawing  pencil. 

^    8.  Pencil  pointer. 

y  9.  Bottle  of  drawing  ink. 

10.  Penholder,  assorted  writing  pens,  and  penwiper. 

-^  11.  French  curves. 

•^12.  Pencil  eraser. 

^  13.  Drawing  paper,  to  suit. 

To  these  may  added: 

14.  Cleaning  rubber. 

15.  Hard  Arkansas  oil  stone. 

16.  Protractor. 

17.  Bottle  holder. 

18.  Piece  of  soapstone. 

19.  2-ft.  or  4-ft.  rule.. 

20.  Sketch  book. 

21.  Erasing  shield. 

22.  Dusting  cloth. 

23.  Lettering  triangle. 

The  student  should  mark  all  his  instruments  and  materials  plainly 
with  initials  or  name,  as  soon  as  purchased  and  approved. 

(1)  All  modern  high-grade  instruments  are  made  with  some 
form  of  l 'pivot  joint,"  originally  invented  by  Theodore  Alteneder 
in  1850  and  again  patented  in  1871.  Before  this  time,  and  by 


FIG.  1. — Tongue  joint.  FIG.  2.— Pivot  joint  (Alteneder). 

other  makers  during  the  life  of  the  patent,  the  heads  of  compasses 
and  dividers  were  made  with  tongue  joints,  as  illustrated  in 
Fig.  1,  and  many  of  these  old  instruments  are  still  in  existence. 


ENGINEERING  DRAWING 


A  modified  form  of  this  pin  joint  is  still  used  for  some  of  the 
cheap  grades  of  instruments.  The  objection  which  led  to  the 
abandonment  of  this  form  was  that  the  wear  of  the  tongue  on 
the  pin  gave  a  lost  motion,  which  may  be  detected  by  holding  a 
leg  in  each  hand  and  moving  them  slowly  back  and  forth.  This 


A.  B  Co 

FIG.  3.— Sections  of  pivot  joints. 

jump  or  lost  motion  after  a  time  increases  to  such  an  extent  as 
to  render  the  instrument  unfit  for  use.  The  pivot  joint,  Fig.  2, 
overcomes  this  objection  by  putting  the  wear  on  the  conical 
points  instead  of  the  through  pin. 

Since  the  expiration  of  the  patent  all  instrument  makers  have 
adopted  this  type  of  head,   and  several  modifications  of  the 


FIG.  4. — The  three  patterns. 

original  have  been  introduced.     Sectional  views  of  the  different 
pivot  joints  are  shown  in  Fig.  3. 

The  handle  attached  to  the  yoke  while  not  essential  to  the 
working  of  the  joint  is  of  great  convenience.  Not  all  instruments 
with  handles,  however,  are  pivot-joint  instruments.  Several 


THE  SELECTION  OF  INSTRUMENTS  7 

straightener  devices  for  keeping  the  handle  erect  have  been 
devised,  but  as  they  interfere  somewhat  with  the  smooth  work- 
ing of  the  joint,  they  are  not  regarded  with  favor  by  experienced 
draftsmen. 

There  are  three  different  patterns  or  shapes  in  which  modern 
compasses  are  made;  the  regular,  the  cylindrical  and  the  Richter, 
Fig.  4.  The  choice  of  shapes  is  entirely  a  matter  of  personal 
preference.  After  one  has^'become  accustomed  to  the  balance 


FIG.  5. — Test  for  alignment. 

and  feel  of  a  certain  instrument  he  will  not  wish  to  exchange  it 
for  another  shape. 

A  favorite  instrument  with  draftsmen,  not  included  in  the 
usual  college  assortment,  is  the  3  1/2-inch  compass  with  fixed 
pencil  point,  and  its  companion  with  fixed  pen  point. 

Compasses  may  be  tested  for  accuracy  by  bending  the  knuckle 
joints  and  bringing  the  points  together  as  illustrated  in  Fig.  5. 
If  out  of  alignment  they  should  not  be  accepted, 
-•dividers  are  made  either  "  plain, "  as  those  in  Fig.  4,  or  "hair- 
spring,"  shown  in  Fig.  6.  The  latter  form,  which  has  one  leg 
with  screw  adjustment,  is  occasionally  of  great  convenience  and 


FIG.  6. — Hairspring  dividers. 

should  be  preferred.     Compasses  may  be  had  also  with  hair- 
spring attachment  on  the  needle-point  leg. 

Ruling  pens  (sometimes  called  right  line  pens)  are  made  in  a 
variety  of  forms.  An  old  type  has  the  upper  blade  hinged  for 
convenience  in  cleaning.  It  is  open  to  the  serious  objection 
that  wear  in  the  joint  will  throw  the  nib  out  of  position,  and  the 
only  remedy  will  be  to  solder  the  joint  fast.  The  improved  form 


8 


ENGINEERING  DRAWING 


has  a  spring  blade  opening  sufficiently  wide  to  allow  of  cleaning, 
Fig.  7.  A  number  are  made  for  resetting  after  cleaning.  Several 
of  these  are  illustrated  in  Fig.  8.  The  form  shown  at  (e)  is 
known  as  a  detail  pen  or  Swede  pen.  For  large  work  this  is  a 
very  desirable  instrument.  Ivory  or  bone  handles  break  easily 
and  on  this  account  should  not  be  purchased.  The  nibs  of  the 


D 


FIG.  7. — Ruling  pen,  with  spring  blade. 

pen  should  be  shaped  as  shown  in  Fig.  434.  Cheap  pens  often 
come  from  the  factory  with  points  too  sharp  for  use,  and  must  be 
dressed,  as  described  on  page  257,  before  they  can  be  used. 

The  set  of  three  spring  bow  instruments  includes  bow  points 
or  spacers,  bow  pencil,  and  bow  pen.  There  are  two  designs  and 
several  sizes.  The  standard  shape  is  illustrated  in  Fig.  9,  the 


FIG.  8. — Various  pens. 

hook  spring  bow  in  Fig.  10.  Both  these  styles  are  made  with 
a  center  screw,  Fig.  11,  but  this  form  has  not  become  popular 
among  draftsmen.  The  springs  of  the  side  screw  bows  should 
be  strong  enough  to  open  to  the  length  of  the  screw,  but  not  so 
stiff  as  to  be  difficult  to  pinch  together.  The  hook  spring  bow 
has  a  softer  spring  than  the  regular. 


THE  SELECTION  OF  INSTRUMENTS  9 

(2)  Drawing  boards  are  made  of  clear  white  pine  (bass  wood 
has  been  used  as  a  substitute)  cleated  to  prevent  warping. 
Care  should  be  taken  in  their  selection.  In  drafting-rooms 


FIG.  9. — Spring  bow  instruments. 


FIG.  10. — Hook-spring  bow  instruments. 


FIG.  11. — Center  screw  bow. 


drawing  tables  with  pine  tops  are  generally  used  instead  of  loose 
boards. 

(3)  The  T-square  with  fixed  head,  Fig.  12,  is  used  for  all 
ordinary  work.  It  should  be  of  hard  wood,  the  blade  perfectly 
straight,  although  it  is  not  necessary  that  the  head  be  absolutely 


10 


ENGINEERING  DRAWING 


square  with  the  blade.  In  a  long  square  it  is  preferable  to  have 
the  head  shaped  as  at  B.  Fig.  13  is  the  English  type,  which  is 
objectionable  in  that  the  lower  edge  is  apt  to  disturb  the  eyes' 
sense  of  perpendicularity.  In  an  office  equipment  there  should 
always  be  one  or  more  adjustable  head  squares,  Fig.  14.  The 


A 


M 

J\ 


FIG.  12. — Fixed  head  T-squares. 


T-square  blade  may  be  tested  for  straightness  by  drawing  a  sharp 
line  with  it,  then  reversing  the  square. 

(4)  Triangles  (sometimes  called  set  squares)  are  made  of  pear 
wood  or  cherry,  mahogany  with  ebony  edges>  hard  rubber,  and 
transparent  celluloid.  The  latter  are  much  to  be  preferred  for 


FIG.  13.— English  T-square. 

a  variety  of  reasons,  although  they  have  a  tendency  to  warp. 
Wooden  triangles  cannot  be  depended  upon  for  accuracy,  and 
hard  rubber  should  not  be  tolerated.  For  ordinary  work  a 
6"-  or  8"-45  degree  and  a  10"-60  degree  are  good  sizes.  A  small 
triangle,  67  1/2  degrees  to  70  degrees,  will  be  of  value  for  drawing 


THE  SELECTION  OF  INSTRUMENTS 


11 


guide  lines  in  slant  lettering.  Triangles  may  be  tested  for 
accuracy  by  drawing  perpendicular  lines  as  shown  in  Fig.  15. 
The  angles  may  be- proven  by  constructing  45-  and  60-degree 
angles  geometrically. 


FIG.  14. — Adjustable  head  T-squares. 


// 

IA\ 

0     O 

0 

0     0 

O    1 

1 

FIG.  15. — To  test  a  triangle. 


(5)  Scales. 

There  are  two  kinds  of  modern  scales,  the  "engineers'  scale" 
of  decimal  parts,  Fig.  16,  and  the  "architects'  scale"  of  propor- 
tional feet  and  inches,  Fig.  17.  The  former  is  used  for  plotting 


12  ENGINEERING  DRAWING 

and  map  drawing,  and  in  the  graphic  solution  of  problems,  the 
latter  for  all  machine  and  structural  drawings.  Scales  are 
usually  made  of  boxwood,  sometimes  of  metal  or  paper,  and  of 
shapes  shown  in  section  in  Fig.  18.  The  triangular  form  (a)  is 
perhaps  the  commonest.  Its  only  advantage  is  that  it  has  more 

\\u\\\\\\y  \\\\\  \u\\\\\\\\\\\\  \u\\\\\  y\\\\\\  \\y\\\\\\\  v\v 

\      09        os       M       vs        zs        oc        ev       9V       W zv        ov-       Bg        ye       V€        M 

^  XAAAAM^^^ 

FIG.  16. — Engineers'  scale. 

scales  on  one  stick  than  the  others,  but  this  is  offset  by  the  delay 
in  finding  the  scale  wanted.  Flat  scales  are  much  more  con- 
venient, and  should  be  chosen  on  this  account.  Three  flat  scales 
are  the  equivalent  of  one  triangular  scale.  The  "  opposite  bevel" 
scale  (e)  is  easier  to  pick  up  than  the  regular  form  (d).  Many 


v^Yvvv^vyvyvv^^ 

V~ V ] * 3 4 W-W " ^T 

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FIG.  17. — Architects'  scale. 

professional  draftsmen  use  a  set  of  6  or  8  scales,  each  graduated 
in  one  division  only,  as  Fig.  19. 

For  the  student  two  12"  flat  scales,  one  graduated  in  inches 
and  sixteenths,  and  3"  and  1  1/2",  the  other  1",  1/2",  1/4",  1/8", 
will  serve  for  all  ordinary  work.  The  usual  triangular  scale 


contains  in  addition  to  these,  3/4",  3/8",  3/16"  and  3/32",  and 
third  flat  scale  with  these  divisions  may  be  added  when  needed. 
(6)  The  best  thumb  tacks  are  made  with  thin  German  silver 
head  and  steel  point  screwed  into  it  (a)  Fig.  20,  and  cost  as  high 
as  seventy-five  cents  a  dozen.  The  ordinary  stamped  tacks  (b) 


THE  SELECTION  OF  INSTRUMENTS  13 

thirty  cents  a  hundred  answer  every  purpose.  Tacks  with  com- 
paratively short,  tapering  pins  should  be  chosen.  Instead  of 
thumb  tacks  many  draftsmen  prefer  1/2-  or  1-oz.  copper  tacks, 
but  they  are  not  recommended  for  students'  use. 

(7)  Drawing  pencils  are  graded  by  letters  from  6B  (very  soft 
and  black)  5B,  4B,  3B,  2B,  B,  HB,  F,  H,  2H,  3H,  4H,  5H,  6H, 
to  8H  (extremely  hard).  For  line  work  6H  is  generally  used. 
A  softer  pencil  (2H)  should  be  used  for  lettering,  sketching  and 


\\XX£TT\  x    \ 

N    \   x 

\   v 

\  v 

\  v 

\  x  \\   \ 

«v                     \\                  V\« 

I    \\ 

i 

///////>/////   /    / 

/    7   / 

;  / 

7  / 

7  / 

7    LA 

7    7 

/    TJ 

FIG.  19. — Single  scale  from  a  set. 

penciling  not  to   be   inked.     Koh-i-noor   or  Faber  are  recom- 
mended.    Many  prefer  a  holder  known  as  an  "artists'  pencil." 

(8)  A  sandpaper  pencil  pointer  or  flat  file  should  always  be  at 
hand  for  sharpening  the  leads. 

(9)  Drawing  ink  is  finely  ground  carbon  in  suspension,  with 
shellac  added  to  render  it  waterproof.     The  non-waterproof  ink 
flows  more  freely,  but  smudges  very  easily. 

Formerly  all  good  drawings  were  made  with  stick  ink,  rubbed 
up  for  use  with  water  in  a  slate  slab,  and  for  very  fine  line  work 
this  is  still  preferred  as  being  superior  to  liquid  ink.  When 


FIG.  20. 

used  in  warm  weather  a  few  drops  of  acetic  acid  or  oxgall  should 
be  added  to  prevent  flies  from  eating  it.  A  fly  can  eat  up  a  line 
made  of  good  Chinese  ink  as  fast  as  it  leaves  the  pen. 

(10)  The  penholder  should  have  a  cork  grip  small  enough  to 
enter  the  mouth  of  ink  bottle.  An  assortment  of  pens  for  letter- 
ing, grading  from  coarse  to  fine  may  be  chosen  from  the  following: 

(Coarse)  Leonardos  ball  points  506  F,  516  F,  516  EF,  or  Gillott 
1032,  1087,  Spencerian  No.  21,  Esterbrook  788,  802,  805. 


14  ENGINEERING  DRAWING 

(Medium)  Spencerian  No.  1,  Gillott  604,  1050. 

(Fine)  Gillott  No.  1,  303,  170. 

(Very  fine)  For  mapping  and  similar  work,  Gillott  431,  290, 
291  and  tit  quill. 

A  penwiper  of  lintless  cloth  or  thin  chamois  skin  should  always 
be  at  hand  for  both  writing  and  ruling  pens. 


FIG.  21. — Curve. 


(11)  Curved  rulers,  called  irregular  curves,  or  French  curves, 
are  used  for  curved  lines  other  than  circle  arcs.  Celluloid  is  the 
only  material  to  be  considered.  The  patterns  for  these  curves 
are  laid  out  in  parts  of  ellipses  and  spirals  or  other  mathematical 
curves  in  combinations  which  will  give  the  closest  approximation 
to  curves  likely  to  be  met  with  in  practice.  For  the  student,  one 
ellipse  curve,  of  the  general  shape  of  Fig.  21,  and  one  spiral, 


PIG.  22. — Logarithmic  spiral  curve. 

either  a  log.  spiral,  Fig.  22,  or  one  similar  to  the  one  used  in  Fig. 
65,  will  be  sufficient.  It  has  been  found  by  experiments  that 
the  curve  of  the  logarithmic  spiral  is  a  closer  approximation  to 
the  cycloid  and  other  mathematical  curves  than  any  other  simple 
curve. 

Sometimes  it  is  advisable  for  the  draftsman  to  make  his  own 


THE  SELECTION  OF  INSTRUMENTS  15 

templet  for  special  or  recurring  curves.  These  may  be  cut  out 
of  thin  holly  or  bass  wood,  sheet  lead,  celluloid,  or  even  card- 
board or  pressboard. 

Flexible  curved  rulers  of  different  kinds  are  sold.  A  copper 
wire  or  piece  of  wire  solder  has  been  used  as  a  home-made 
substitute. 

The  curve  illustrated  in  Fig.  23  has  been  found  particularly 
useful  for  engineering  diagrams,  steam  curves,  etc.  It  is  plotted 
on  the  polar  equation  r  =A  cos  0  +  K,  in  which  A  may  be 
about  5  I/ 2"  and  K  8". 

(12)  The  ruby  pencil  eraser  is  the  favorite  at  present.  One 
of  large  size,  with  beveled  end  is  preferred.  This  eraser  is  much 


FIG.  23. 

better  for  ink  than  a  so-called  ink  eraser,  as  it  will  remove  the 
ink  perfectly  without  destroying  the  surface  of  paper  or  cloth. 
A  piece  of  soft  "  H  "  rubber,  or  sponge  rubber  is  useful  f Or  cleaning 
paper. 

(13)  Drawing  paper  is  made  in  a  variety  of  qualities,  white  for 
finished  drawings  and  cream  or  buff  tint  for  detail  drawings. 
It  may  be  had  either  in  sheets  or  rolls.  In  general,  paper  should 
have  sufficient  grain  to  " tooth"  to  take  the  pencil,  be  agreeable 
to  the  eye,  and  have  good  erasing  qualities.  In  white  paper  the 
brands  known  as  "Normal"  and  "Napoleon"  have  these 
qualities.  For  wash  drawings  Whatman's  paper  should  be  used, 
and  for  fine  line  work  for  reproduction  Reynold's  Bristol  board. 
These  are  both  English  papers  in  sheets,  whose  sizes  may  be 
found  listed  in  any  dealer's  catalogue.  Whatman's  is  a  hand- 
made paper  in  three  finishes,  H,  C.P.,  and  R,  or  hot  pressed, 
cold  pressed,  and  rough;  the  first  for  fine  line  drawings,  the  second 
for  either  ink  or  color,  and  the  third  for  water  color  sketches. 
The  paper  in  the  larger  sheets  is  heavier  than  in  the  smaller  sizes, 
hence  it  is  better  to  buy  large  sheets  and  cut  them  up.  Bristol 
board  is  a  very  smooth  paper,  made  in  different  thicknesses, 


16 


ENGINEERING  DRAWING 


2-ply,  3-ply,  4-ply,  etc.;  3-ply  is  generally  used.  For  working 
drawings  the  cream  or  buff  detail  papers  are  much  easier  on  the 
eyes  than  white  papers.  The  cheap  manilla  papers  should  be 
avoided.  A  few  cents  more  per  yard  is  well  spent  in  the  increased 
comfort  gained  from  working  on  good  paper.  In  buying  in 
quantity  it  is  cheaper  to  buy  roll  paper  by  the  pound.  For  maps 


FIG.  24. — Railroad  pen.  FIG.  25. — Double  pen.         FIG.  26. — Curve  pen. 

or  other  drawings  which  are  to  withstand  hard  usage,  mounted 
papers,  with  cloth  backing  are  used.  Drawings  to  be  duplicated 
by  blue  printing  are  made  on  bond  or  ledger  papers,  or  traced  on 
tracing  paper  or  tracing  cloth.  Tracing  and  the  duplicating 
processes  are  described  in  Chapter  XIII. 

The  foregoing  instruments  and  materials  are  all  that  are  needed 
in  ordinary  practice,  and  are  as  a  rule,  with  the  exception  of 
paper,  pencils,  ink,  erasers,  etc.,  classed  as  supplies,  what  a 


THE  SELECTION  OF  INSTRUMENTS 


17 


draftsman   is  expected   to   take   with   him   into   a   commercial 
drafting  room. 

There  are  many  other  special  instruments  and  devices  not 
necessary  in  ordinary  work.     With  some  of  these  the  draftsman 


FIG.  27. — Lettering  pens. 

should  be  familiar,  as  they  may  be  very  convenient  in  some 
special  cases,  and  are  often  found  as  part  of  a  drafting  room 
equipment. 

The  railroad  pen  is  used  for  double  lines.     In  selecting  this 


FIG.  28. — Proportional  dividers. 

pen  notice  that  the  pens  are  turned  as  illustrated  in  Fig.  24. 
Most  forms  have  the  pens  in  opposite  directions.  A  much  better 
pen  for  double  lines  up  to  1/4"  apart  is  the  border  pen,  Fig.  25, 
as  it  can  be  held  down  to  the  paper  more  satisfactorily.  It  may 


FIG.  29. — Beam  compass. 

be  used  for  very  wide  solid  lines  by  inking  the  middle  space  as 
well  as  the  two  pens. 

The  curve  pen,  Fig.  26,  made  with  a  swivel,  for  freehand  curves, 
contours,  etc.,  is  of  occasional  value. 
2 


18 


ENGINEERING  DRAWING 


Payzant  pens,  Fig.  27A,  for  large  single  stroke  lettering  save  a 
great  deal  of  time.  They  are  made  in  sizes  from  \  to  6.  Fig. 
27  B  is  the  Shepard  pen,  made  for  the  same  purpose. 

Proportional  dividers,  for  enlarging  or  reducing  in  any  propor- 


FIG.  30. — Drop  pen. 


tion,  Fig.  28,  are  used  in  map  work,  patent  office  drawings,  etc. 
The  divisions  marked  "lines"  are  linear  proportions,  those 
marked  "circles"  give  the  setting  for  dividing  a  circle  whose 
diameter  is  measured  by  the  large  end  into  the  desired  number 
of  equal  parts. 


FIG.  31.— Protractor. 


The  beam  compass  is  used  for  circles  larger  than  the  capacity 
of  the  compass  and  lengthening  bar.  A  good  form  is  illustrated 
in  Fig.  29.  The  bar  with  shoulder  prevents  the  parts  from 
turning  or  falling  off. 


THE  SELECTION  OF  INSTRUMENTS 


19 


With  the  "  drop  pen  "  or  rivet  pen  smaller  circles  can  be  made, 
and  made  much  faster  than  with  the  bow  pen.  It  is  held  as 
shown  in  Fig.  30,  the  needle  point  stationary  and  the  pen  revolving 
around  it.  It  is  of  particular  convenience  in  bridge  and  structural 
work,  and  in  topographical  drawing. 


FIG.  32. — Section  liner. 


A  protractor  is  a  necessity  in  map  and  topographical  work. 
A  semicircular  brass  or  German  silver  one,  6"  diameter,  such  as 
Fig.  31,  will  read  to  half  degrees.  They  may  be  had  with  an  arm 
and  vernier  reading  to  minutest 


D 


D 


FIG.  33. — Section  lining  devices. 


Section  lining  or  " cross  hatching"  is  a  difficult  operation  for 
the  beginner,  but  is  done  almost  automatically  by  the  experienced 
draftsman.  Several  instruments  for  mechanical  spacing  have 
been  devised.  For  ordinary  work  they  are  not  worth  the  trouble 


20 


ENGINEERING  DRAWING 


of  setting  up,  and  a  draftsman  should  never  become  dependent 
upon  them,  but  they  are  of  limited  value  for  careful  drawing  for 
reproduction.  One  form  is  shown  in  Fig.  32. 

A  home-made  device  may  be  made  of  a  piece  of  thin  wood  or 


FIG.  34. — Universal  drafting  machine. 


celluloid  cut  in  one  of  the  shapes  shown  in  Fig.  33,  and  used  by 
slipping  the  block  and  holding  the  triangle,  then  holding  the 
block  and  moving  the  triangle. 

There  are  several  machines  on  the  market  designed  to  save  time 


FIG.  35.— Dotting  pen. 


and  trouble  in  drawing.  The  best  known  is  the  Universal 
Drafting  Machine  illustrated  in  Fig.  34.  This  machine,  which 
combines  the  functions  of  T-square,  triangle,  scale  and  protractor, 
has  had  the  test  of  ten  years'  use,  and  is  used  extensively  in  large 


THE  SELECTION  OF  INSTRUMENTS 


21 


drafting  rooms,  and  by  practising  engineers  and  architects.  It 
has  been  estimated  that  25%  of  time  in  machine  drawing  and 
over  50  %  in  civil  engineering  work  is  saved  by  its  use. 

Vertical  drawing  boards  with  sliding  parallel  straight  edges 
.are  preferred  by  some  for  large  work. 


FIG.  36. 


FIG.  37. 


Several  kinds  of  dotting  pens  have  been  introduced.  The 
•one  illustrated  in  Fig.  35  is  perhaps  the  best.  When  carefully 
handled  it  works  successfully,  and  will  make  five  different  kinds 
<of  dotted  and  dashed  lines.  The  length  of  the  short  dots  may 


FIG.  38. 


FIG.  39. 


be  varied  by  a  slight  inclination  of  the  handle.  For  special  work 
requiring  a  great  many  dotted  lines  it  might  prove  to  be  a  good 
investment. 

A  number  of  different  forms  of  patented  combination  "tri- 


22 


ENGINEERING  DRAWING 


angles"  have  been  devised.     Of  these  the  best  known  are  the 

Kelsey,  Fig.  36,  the  Rondinella,  Fig.  37,  and  the  Zange,  Fig.  38. 

Bottle  holders  prevent  the  possibility  of  ruining  the  drawing, 

table  or  floor  by  the  upsetting  of  the  ink  bottle.     Fig.  39  is  a 


FIG.  40. 


usual  form,  Fig.  40  a  novelty  by  the  Alteneder  Co.  by  whose  aid 
the  pen  may  be  filled  with  one  hand  and  time  saved  thereby. 

Erasing  shields  of  metal  or  celluloid,  meant  to  protect  the 
drawing  while  an  erasure  is  being  made,  are  sold.  Slots  for  the 
purpose  may  be  cut  as  needed  from  sheet  celluloid  or  tough  paper. 


CHAPTER  III. 

THE  USE  OF  INSTRUMENTS. 

In  beginning  the  use  of  drawing  instruments  particular  atten- 
tion should  be  paid  to  correct  method  in  their  handling.  There 
are  many  instructions  and  cautions,  whose  reading  may  seem 
tiresome,  and  some  of  which  may  appear  trivial,  but  the  strict 
observance  of  all  these  details  is  really  necessary,  if  one  would 
become  proficient  in  the  art. 

Facility  will  come  with  continued  practice,  but  from  the  outset 
good  form  must  be  insisted  upon.  One  might  learn  to  write 
fairly,  holding  the  pen  between  the  fingers  or  gripped  in  the  closed 
hand,  but  it  would  be  poor  form.  It  is  just  as  bad  to  draw  in 
poor  form  as  to  write  in  poor  form.  Bad  form  in  drawing  is 
distressingly  common,  and  may  be  traced  in  every  instance  to 
lack  of  care  or  knowledge  at  the  beginning,  and  the  consequent 
formation  of  bad  habits.  These  habits  when  once  formed  are 
most  difficult  to  overcome. 

All  the  mechanical  drawing  we  do  serves  incidentally  for 
practice  in  the  use  of  instruments,  but  it  is  best  for  the  beginner 
to  learn  the  functions  and  become  familiar  with  the  handling  and 
feel  of  each  of  his  instruments  by  drawing  two  or  three  plates 
designed  solely  for  that  purpose,  so  that  when  real  drawing 
problems  are  assigned  the  use  of  the  instruments  will  be  easy  and 
natural,  and  there  need  be  no  distraction  nor  loss  of  time  on 
account  of  correction  for  faulty  manipulation. 

Thus  while  the  drawings  are  worth  nothing  when  finished 
except  to  show  the  student's  proficiency  and  skill,  some  such 
figures  as  those  on  pages  42  and  45  should  be  practised  until  he 
feels  a  degree  of  ability  and  assurance,  and  is  no^  afraid  of  his 
instruments. 

As  these  figures  are  for  discipline  and  drill,  the  instructor  should 
not  accept  a  plate  with  the  least  inaccuracy,  blot,  blemish,  or 
indication  of  ink  erasure.  It  is  a  mistaken  kindness  to  the 
beginner  to  accept  faulty  or  careless  work.  The  standard  set  at 
this  time  will  be  carried  through  his  professional  life,  and  he 

23 


24 


ENGINEERING  DRAWING 


should  learn  that  a  good  drawing  can  be  made  just  as  quickly 
as  a  poor  one.  Erasing  is  expensive  and  mostly  preventable, 
and  the  student  allowed  to  continue  in  a  careless  way  will  grow 
to  regard  his  eraser  and  jack  knife  as  the  most  important  tools 
in  his  kit.  The  draftsman  of  course  erases  an  occasional  mistake, 
and  instructions  in  making  corrections  may  be  given  later  in 
the  course,  but  these  first  plates  must  not  be  erased. 

Preparation  for  Drawing. 

The  drawing  table  should  be  set  so  that  the  light  comes  from 
the  left,  and  adjusted  to  a  convenient  height  for  standing,  that 
is,  from  36  to  40  inches,  with  the  board  inclined  at  a  slope  of 
about  1  to  8.  One  may  draw  with  more  freedom  standing  than 
sitting. 

The  Pencil. 

The  pencil  must  be  selected  with  reference  to  the  kind  of  paper 
used.  For  line  drawing  on  paper  of  such  texture  as  "  Normal " 
a  pencil  as  hard  as  6H  may  be  used,  while  on  Bristol,  for  example, 
a  softer  one  would  be  preferred.  Sharpen  it  to  a  long  point  as 
in  Fig.  41  removing  the  wood  with  the  penknife  and  sharpening 
the  lead  by  rubbing  it  on  the  sand  paper  pad.  A  flat  or  wedge 


FIG.  41. — A  wedge  point. 

point  will  not  wear  away  in  use  as  fast  as  a  conical  point,  and  on 
that  account  is  preferred  for  straight  line  work  by  most  drafts- 
men. By  oscillating  the  pencil  slightly  while  rubbing  the  lead 
on  two  opposite  sides,  an  elliptical  section  is  obtained.  A  softer 
pencil  (2H)  should  be  at  hand,  sharpened  to  a  long  conical  point 
for  sketching  and  lettering.  Have  the  sand  paper  pad  within 
reach  and  keep  the  pencils  sharp.  Pencil  lines  should  be  made 
lightly,  but  sufficiently  firm  and  sharp  to  be  seen  distinctly 
without  eye  strain,  for  inking  or  tracing.  The  beginner's  usual 
mistake  in  using  a  hard  pencil  is  to  cut  tracks  in  the  paper.  Too 


THE  USE  OF  INSTRUMENTS 


25 


much  emphasis  cannot  be  given  to  the  importance  of  clean, 
careful,  accurate  penciling.  Never  permit  the  thought  that  poor 
penciling  may  be  corrected  in  inking. 

The  T-Square. 

The  T-square  is  used  only  on  the  left  edge  of  the  drawing 
board  (an  exception  to  this  is  made  in  the  case  of  a  left-handed 
person,  whose  table  should  be  arranged  with  the  light  coming 
from  the  right  and  the  T-square  used  on  the  right  edge). 

Since  the  T-square  blade  is  more  rigid  near  the  head  than 
toward  the  outer  end,  the  paper,  if  much  smaller  than  the  size 
of  the  board,  should  be  placed  close  to  the  left  edge  of  the  board 
(within  an  inch  or  so)  with  its  lower  edge  several  inches  from  the 
bottom.  With  the  T-square  against  the  left  edge  of  the  board, 


FIG.  42. 

square  the  top  of  the  paper  approximately,  hold  in  this  position, 
slipping  the  T-square  down  from  the  edge,  and  put  a  thumb  tack 
in  each  upper  corner,  pushing  it  in  up  to  the  head;  move  the 
T-square  down  over  the  paper  to  smooth  out  possible  wrinkles 
and  put  thumb  tacks  in  the  other  two  corners. 

The  T-square  is  used  manifestly  for  drawing  parallel  horizontal 
lines.  These  lines  should  always  be  drawn  from  left  to  right, 
consequently  points  for  their  location  should  be  marked  on  the 
left  side;  vertical  lines  are  drawn  with  the  triangle  set  against 
the  T-square,  always  with  the  perpendicular  edge  nearest  the 


26 


ENGINEERING  DRAWING 


head  of  the  square  and  toward  the  light.  These  lines  are  always 
drawn  up  from  bottom  to  top,  consequently  their  location  points 
should  be  made  at  the  bottom. 

In  drawing  lines  great  care  must  be  exercised  in  keeping  them 
accurately  parallel  to  the  T-square  or  triangle,  holding  the  pencil 
point  lightly,  but  close  against  the  edge,  and  not  varying  the 
angle  during  the  progress  of  the  line. 

The  T-square  is  adjusted  by  holding  it  in  the  position  either 
of  Fig.  42  the  thumb  up,  and  fingers  touching  the  board  under 


FIG.  43. 

the  head,  or  of  Fig.  43,  the  fingers  on  the  blade  and  the  thumb  on 
the  board.  In  drawing  vertical  lines  the  T-square  is  held  in 
position  against  the  left  edge  of  the  board,  the  thumb  on  the 
blade,  while  the  fingers  of  the  left  hand  adjust  the  triangle,  as 
illustrated  in  Fig.  44.  One  may  be  sure  the  T-square  is  in  contact 
with  the  board  by  hearing  the  little  double  click  as  it  comes 
against  it. 

Laying  off  the  Drawing. 

The  paper  is  usually  cut  somewhat  larger  than  the  desired 
size  of  the  drawing,  and  is  trimmed  to  size  after  the  work  is 
finished.  Suppose  the  plate  is  to  be  9"  x  12"  with  a  half-inch 


THE  USE  OF  INSTRUMENTS 


27 


border.  Near  the  lower  edge  of  the  paper  draw  a  horizontal  line, 
and  near  the  left  edge  a  vertical  line.  If  the  lower  left-hand 
corner  of  the  board  is  known  to  be  square  these  long  vertical 
lines  may  be  drawn  with  the  T-square  thrown  around  against 
the  lower  edge.  With  the  scale  flat  on  the  paper  mark  off  on 
these  lines  the  length  and  width  of  the  finished  plate,  and  points 


FIG.  44. 

for  the  border  1/2"  inside  these  marks.  Draw  lines  through  these 
points  giving  the  trimming  line  and  the  border  line.  These 
"  points  "  should  not  be  dots,  or  holes  bored  with  the  pencil,  but 
short,  light  dashes. 

Use  of  Dividers. 

Suppose  the  space  inside  the  border  is  to  be  divided  into  six 
equal  parts  by  bisecting  the  left  border  line  and  dividing  the 
lower  border  line  into  three  parts.  These  divisions  are  made  not 
with  the  scale  but  with  the  dividers.  Facility  in  the  use  of  this 


28  ENGINEERING  DRAWING 

instrument  is  most  essential,  and  quick  and  absolute  control  of 
its  manipulation  must  be  gained.  It  should  be  opened  with  one 
hand  by  pinching  in  the  chamfer  with  the  thumb  and  second 
finger.  This  will  throw  it  into  correct  position  with  the  thumb 
and  forefinger  on  the  outside  of  the  legs  and  the  second  and  third 
finger  on  the  inside,  with  the  head  resting  just  above  the  second 
joint  of  the  forefinger,  Fig.  45.  It  is  thus  under  perfect  control, 


FIG.  45. 

with  the  thumb  and  forefinger  to  close  it  and  the  other  two  to 
open  it.  This  motion  should  be  practised  until  an  adjustment 
to  the  smallest  fraction  can  be  made.  In  coming  down  to  small 
divisions  the  second  and  third  fingers  must  be  gradually  slipped 
out  from  between  the  legs  while  they  are  closed  down  upon  them. 

To  Divide  a  Line,  by  Trial. 

In  bisecting  a  line  the  dividers  are  opened  roughly  at  a  guess 
to  one-half  the  length.  This  distance  is  stepped  off  on  the  line, 
holding  the  instrument  by  the  handle  with  the  thumb  and  fore- 
finger. If  the  division  be  short  the  leg  should  be  thrown  out  to 
one-half  the  remainder,  estimated  by  the  eye,  without  removing 
the  other  leg  from  its  position  on  the  paper,  and  the  line  spaced 
again  with  this  setting,  Fig.  46.  If  this  should  not  come  out 
exactly  the  operation  may  be  repeated.  With  a  little  experience 
a  line  may  be  divided  in  this  way  very  rapidly.  Similarly  a  line 
may  be  divided  into  any  number  of  equal  parts,  say  five,  by 
estimating  the  first  division,  stepping  this  lightly  along  the 
line,  with  the  dividers  held  vertically  by  the  handle,  turning  the 
instrument  first  in  one  direction  and  then  in  the  other.  If  the 
last  division  fall  short,  one-fifth  of  the  remainder  should  be  added 


THE  USE  OF  INSTRUMENTS  29 

by  opening  the  dividers,  keeping  the  one  point  on  the  paper. 
If  the  last  division  be  over,  one  fifth  of  the  excess  should  be  taken 
off  and  the  line  respaced.  If  it  is  found  difficult  to  make  this 
small  adjustment  accurately  with  the  fingers,  the  hairspring 
may  be  used.  It  will  be  found  more  convenient  to  use  the  bow 


FIG.  46.— Bisecting  a  line. 

spacers  instead  of  the  dividers  for  small  or  numerous  divisions. 
Avoid  pricking  unsightly  holes  in  the  paper.  The  position  of  a 
small  prick  point  may  be  preserved  if  necessary  by  drawing  a 
little  ring  around  it  with  the  pencil. 

Use  of  the  Triangles. 

We  have  seen  that  vertical  lines  are  drawn  with  the  triangle 
set  against  the  T-square,  Fig.  44.  Usually  the  60-degree  triangle 
is  used,  as  it  has  the  longer  perpendicular.  In  both  penciling  and 
inking,  the  triangles  should  always  be  used  in  contact  with  a 
guiding  straight-edge. 

With  the  T-square  against  the  edge  of  the  board,  lines  at  30 
degrees,  45  degrees  and  60  degrees  may  be  drawn  as  shown  in 
Fig.  47,  the  arrows  showing  the  direction  of  motion.  The  two 
triangles  may  be  used  in  combination  for  angles  of  15,  75,  105 


30 


ENGINEERING  DRAWING 


degrees,  etc.,  Fig.  48.     Thus  any  multiple  of  15  degrees  may  be 
drawn  directly,  and  a  circle  may  be  divided  with  the  45-degree 


FIG.  47. 


triangle  into  4  or  8  parts,  with  the  60-degree  triangle  into  6  or 
12  parts,  and  with  both  into  24  parts. 
To  draw  a  parallel  to  any  line,  Fig.  49,  adjust  to  it  a  triangle 


FIG.  48. 


held  against  the  T-square  or  other  triangle,  hold  the  guiding  edge 

in  position  and  slip  the  first  triangle  on  it  to  the  required  position. 

To  draw  a  perpendicular  to  any  line,  Fig.  50,  fit  the  hypothenuse 


THE  USE  OF  INSTRUMENTS 


31 


of  a  triangle  to  it,  with  one  edge  against  the  T-square  or  other 
triangle,  hold  the  T-square  in  position  and  turn  the  triangle  until 
its  other  side  is  against  the  edge,  the  hypothenuse  will  then  be 
perpendicular  to  the  line.  Move  it  to  the  required  position. 


FIG.  49. — To  draw  parallel  lines. 


Never  attempt  to  draw  a  perpendicular  to  a  line  by  merely 
placing  one  leg  of  the  triangle  against  it.  Never  work  to  the 
extreme  corner  of  a  triangle,  but  keep  the  T-square  away  from 
the  line. 


Fi  G.  50. — To  draw  perpendicular  lines. 


Use  of  the  Compasses. 

The  compass  has  the  same  general  shape  as  the  dividers  and 
is  manipulated  in  a  similar  way.  Its  needle  point  should  first 
of  all  be  adjusted  by  turning  it  with  the  shoulder  point  out, 


32 


ENGINEERING  DRAWING 


inserting  the  pen  in  the  place  of  the  pencil  leg  and  setting  the 
needle  a  trifle  longer  than  the  pen.  The  needle  point  should  be 
kept  in  this  position  so  as  to  be  always  ready  for  the  pen,  and  the 
lead  adjusted  to  it.  The  lead  should  be  sharpened  on  the  sand 


FIG.  51. 


paper  to  a  fine  wedge  or  long  bevel  point.  Radii  should  be 
pricked  off  or  marked  on  the  paper  and  the  pencil  leg  adjusted  to 
the  points.  The  needle  point  may  be  guided  to  the  center  with 
the  little  finger  of  the  left  hand,  Fig.  51.  When  the  lead  is 


FIG.  52. 


FIG.  53. 


adjusted  to  pass  exactly  through  the  mark  the  right  hand  should 
be  raised  to  the  handle  and  the  circle  drawn  (clockwise)  in  one 
sweep  by  turning  the  compass,  rolling  the  handle  with  the  thumb 
and  forefinger,  inclining  it  slightly  in  the  direction  of  the  line, 


THE  USE  OF  INSTRUMENTS 


33 


Fig.  52.  The  position  of  the  fingers  after  the  revolution  is  illus- 
trated in  Fig.  53.  Circles  up  to  perhaps  three  inches  in 
diameter  may  be  -  drawn  with  the  legs  straight  but  for  larger 
sizes  both  the  needle-point  leg  and  the  pencil  leg  should  be  turned 


FIG.  54. 


at  the  knuckle  joints  so  as  to  be  perpendicular  to  the  paper, 
Fig.  54.  The  5  1/2-inch  compass  may  be  used  in  this  way  for 
circles  up  to  perhaps  ten  inches  in  diameter;  larger  circles  are 
made  by  using  the  lengthening  bar,  as  illustrated  in  Fig.  55.  In 


FIG.  55. — Use  of  lengthening  bar. 


drawing  concentric  circles  the  smallest  should  always  be  drawn 
first. 

The  bow  instruments  are  us^L  for  small  circles,  particularly 
when  a  number  are  to  be  macto^Mhe  same  diameter.     In  chang- 
3  -*4fl[ 


34 


ENGINEERING  DRAWING 


ing  the  setting,  to  avoid  wear  and  final  stripping  of  the  thread, 
the  pressure  of  the  spring  against  the  nut  should  be  relieved  by 
holding  the  points  in  the  left  hand  and  spinning  the  nut  in  or  out 
with  the  ringer.  Small  adjustments  should  be  made  with  one 
hand,  with  the  needle  point  in  position  on  the  paper,  Fig.  56. 


FIG.  56. 

Use  of  the  Scale. 

In  representing  objects  which  are  larger  than  can  be  drawn  to 
their  natural  or  full  size  it  is  necessary  to  reduce  the  dimensions 
on  the  drawing  proportionately,  and  for  this  purpose  the  archi- 
tects' scale  is  used.  The  first  reduction  is  to  what  is  commonly 
called  half  size  or  correctly  speaking,  to  the  scale  of  6"  =  1';  that 
is,  each  dimension  is  reduced  one-half.  This  scale  is  used  in 
working  drawings  even  if  the  object  be  only  slightly  larger  than 
could  be  drawn  full  size,  and  is  generally  worked  with  the  full- 
size  scale,  halving  the  dimensions  mentally.  If  this  scale  is  too 

-*--74'. 


FIG.  57. 

large  for  the  paper  the  drawing  is  made  to  the  scale  of  three 
inches  to  the  foot,  often  called  "quarter  size,"  that  is,  three  inches 
measured  on  the  drawing  is  equal  to  one  foot  on  the  object. 
This  is  the  first  scale  of  the  usual  commercial  set,  on  it  the 
distance  of  three  inches  is  divided  into  twelve  equal  parts  and 
each  of  these  subdivided  into  eighths.  This  distance  should 


THE  USE  OF  INSTRUMENTS  35 

be  thought  of  not  as  three  inches  but  as  a  foot  divided  into  inches 
and  eighths  of  inches.  It  is  noticed  that  this  foot  is  divided  with 
the  zero  on  the  inside,  the  inches  running  to  the  left  and  the  feet 
to  the  right,  so  that  dimensions  given  in  feet  and  inches  may  be 
read  directly,  as  2  ft.  7  1/8",  Fig.  57.  On  the  other  end  will  be 
found  the  scale  of  11/2  inches  equals  one  foot,  or  eighth  size, 
with  the  distance  of  one  and  one-half  inches  divided  on  the  right 
of  the  zero  into  twelve  parts  and  subdivided  into  quarter  inches, 
and  the  foot  divisions  to  the  left  of  the  zero,  coinciding  with  the 
marks  of  the  3"  scale. 

,  If  the  1  1/2"  scale  is  too  large  for  the  object,  the  next  commer- 
cial size  is  to  the  scale  of  one  inch  equals  one  foot,  and  so  on 
down  as  shown  in  the  following  table. 

Full  size  3/4"   =  1' 

Scale  6"  =1'  1/2"   =  1' 

4"  =1'  (rarely  used)  3/8"=!' 

3"  =  1'  1/4"   =1' 

2"  =1'  (rarely  used)  3/16" -I/ 

11  /2"  =  1'  1/8"   =1' 

1"  =1'  3/32"- 1' 

The  scale  1/4"  equals  1  ft.  is  the  usual  one  for  ordinary  house 
plans  and  is  often  called  by  architects  the  "quarter  scale." 
This  term  should  not  be  confused  with  the  term  "quarter  size," 
as  the  former  means  1/4"  to  1  ft.  and  the  latter  1/4"  to  1  inch. 

A  circle  is  generally  given  in  terms  of  its  diameter.  To  draw 
it  the  radius  is  necessary.  In  drawing  to  half  size  it  is  thus  often 
convenient  to  lay  off  the  amount  of  the  diameter  with  a  3-in. 
scale  and  to  use  this  distance  as  the  radius. 

As  far  as  possible  successive  measurements  on  the  same  line 
should  be  made  without  shifting  the  scale. 

For  plotting  and  map  drawing  the  "  engineers'  scale  "  of  deci- 
mal parts  10,  20,  30,  40,  50,  60,  80,  100  to  the  inch,  is  used. 
This  scale  should  never  be  used  for  machine  or  structural  work. 
Inking. 

After  being  penciled,  drawings  are  finished  either  by  inking 
on  the  paper,  or  in  the  great  majority  of  work,  by  tracing  in  ink 
on  tracing  cloth.  The  beginner  should  become  proficient  in 
inking  both  on  paper  and  cloth. 

The  ruling  pen  is  never  used  freehand,  but  always  in  connec- 


36 


ENGINEERING  DRAWING 


tion  with  a  guiding  edge,  either  T-square,  triangle,  straight-edge 
or  curve.  The  T-square  and  triangle  should  be  held  in  the  same 
positions  as  for  penciling.  It  is  bad  practice  to  ink  with  the 
triangle  alone. 

To  fill  the  pen  take  it  to  the  bottle  and  touch  the  quill  filler 
between  the  nibs,  being  careful  not  to  get  any  ink  on  the  outside 
of  the  blades.  Not  more  than  three-sixteenths  of  an  inch  should 
be  put  in  or  the  weight  of  the  ink  will  cause  it  to  drop  out  in  a 
blot.  The  pen  should  be  held  as  illustrated  in  Fig.  58,  with  the 
thumb  and  second  finger  in  such  position  that  they  may  be  used 
in  turning  the  adjusting  screw,  and  the  handle  resting  on  the 


FIG.  58. — Holding  the  pen. 

forefinger.  This  position  should  be  observed  carefully,  as  the 
tendency  will  be  to  bend  the  second  finger  to  the  position  in 
which  a  pencil  or  writing  pen  is  held,  which  is  obviously  conveni- 
ent in  writing  to  give  the  up  stroke,  but  as  this  motion  is  not 
required  with  the  ruling  pen  the  position  illustrated  is  preferable. 

For  full  lines  the  screw  should  be  adjusted  to  give  a  strong  line, 
of  the  size  of  the  first  line  of  Fig.  62.  A  fine  drawing  does  not 
mean  a  drawing  made  with  fine  lines,  but  with  uniform  lines, 
and  accurate  joints  and  tangents. 

The  pen  should  be  held  against  the  straight  edge  with  the 
blades  parallel  to  it,  the  handle  inclined  slightly  to  the  right  and 
always  kept  in  a  plane  through  the  line  perpendicular  to  the 
paper.  The  pen  is  thus  guided  by  the  upper  edge  of  the  ruler, 
whose  distance  from  the  pencil  line  will  therefore  vary  with  its 


THE  USE  OF  INSTRUMENTS 


37 


thickness,  and  with  the  shape  of  the  under  blade  of  the  pen,  as 
illustrated  in  enlarged  scale  in  Fig.  59.  If  the  pen  is  thrown  out 
from  the  perpendicular  as  at  B  it  will  run  on  one  blade  and  a  line 
ragged  on  one  side  will  result.  If  turned  in  from  the  perpendicu- 
lar as  at  C  the  ink  is  very  apt  to  run  under  the  edge  and  cause  a 
blot. 

A  line  is  drawn  with  a  whole  arm  movement,  the  hand  resting 
on  the  tips  of  the  third  and  fourth  fingers,  keeping  the  angle  of 
inclination  constant.  Just  before  reaching  the  end  of  the  line 
the  two  guiding  fingers  on  the  straight  edge  should  be  stopped, 


FIG.  59. — Correct  position  at  A. 

and,  without  stopping  the  motion  of  the  pen,  the  line  finished 
with  a  finger  movement.  Short  lines  are  drawn  with  this  finger 
movement  alone.  When  the  end  of  the  line  is  reached  lift  the 
pen  quickly  and  move  the  straight  edge  away  from  the  line. 
The  pressure  on  the  paper  should  be  light,  but  sufficient  to  give 
a  clean  cut  line,  and  will  vary  with  the  kind  of  paper  and  the 
sharpness  of  the  pen,  but  the  pressure  against  the  T-square  should 
be  only  enough  to  guide  the  direction. 

If  the  ink  refuses  to  flow  it  is  because  it  has  dried  and  clogged 
in  the  extreme  point  of  the  pen.  This  clot  or  obstruction  may 
be  removed  by  touching  the  pen  on  the  finger,  or  by  pinching  the 
blade  slightly,  breaking  it  up.  If  it  still  refuses  to  start  it  should 
be  wiped  out  and  fresh  ink  added.  The  pens  must  be  wiped  clean 
after  using  or  the  ink  will  corrode  the  steel  and  finally  destroy 
them. 


38  ENGINEERING  DRAWING 

Instructions  in  regard  to  the  ruling  pen  apply  also  to  the  com- 
pass pen.  It  should  be  kept  perpendicular  by  using  the  knuckle 
joint,  and  the  compass  inclined  slightly  in  the  direction  of  the 
line.  In  adjusting  the  compass  for  an  arc  which  is  to  connect 
other  lines  the  pen  point  should  be  brought  down  very  close  to 
the  paper  without  touching  it  to  be  sure  that  the  setting  is  exactly 
right. 

It  is  a  universal  rule  in  inking  that  circles  and  circle  arcs  must 
be  drawn  first.  It  is  much  easier  to  connect  a  straight  line  to  a 
curve  than  a  curve  to  a  straight  line. 


FIG.  60. 

It  should  be  noted  particularly  that  two  lines  are  tangent  to 
each  other  when  their  centers  are  tangent,  and  not  when  the 
lines  simply  touch  each  other,  thus  at  the  point  of  tangency  the 
width  will  be  equal  to  the  width  of  a  single  line,  Fig.  60  A. 

After  reading  these  paragraphs  the  beginner  had  best  take  a 
blank  sheet  of  paper  and  cover  it  with  ink  lines  of  varying  lengths 
and  weights,  practising  starting  and  stopping  on  penciled  limits, 
until  he  feels  acquainted  with  the  pens.  If  in  his  set  there  are 
two  pens  of  different  sizes  the  larger  one  should  be  used,  as  it  fits 
the  hand  of  the  average  man  better  than  the  smaller  one,  holds 
more  ink,  and  will  do  just  as  fine  work. 

Faulty  Lines. 

If  inked  lines  appear  imperfect  in  any  way  the  reason  should 
be  ascertained  immediately.  It  may  be  the  fault  of  the  pen,  the 
ink,  the  paper,  or  the  draftsman,  but  with  the  probabilities 
greatly  in  favor  of  the  last.  Fig.  61  illustrates  the  characteristic 
appearance  of  several  kinds  of  faulty  lines.  The  correction  in 
each  case  will  suggest  itself. 


THE  USE  OF  INSTRUMENTS  39 

High-grade  pens  usually  come  from  the  makers  well  sharpened. 
Cheaper  ones  often  need  dressing  before  they  can  be  used  satis- 
factorily. If  the  pen  is  not  working  properly  it  must  be  sharp- 
ened as  described  in  Chapter  XIV,  page  257. 


.  ...  i .  .  .,..,.,•,.  Pesifoo  faraway  frv/7?  edge  ofTsgva/e 

-— *— »!-^— -gnaBBHWB^i^HHB^^^B^*  ^en  ^°  C/OS€  ^  e^e  ^  raf?  (/ff(^er 
^^mtf*m^mmm-m^——m^mBmmmmn^^~^i**~  fak  on  oufe/de  0f6/ade,  nyr?  i/fider 
___ _ -~  Penb/ades  nof  kepf para//e/  fo  T*?. 

^—••rrr,  i  n  WJK\  m    iPPi^pPiPii  Tsgvasif  s///petf//7fo  tref///?e 

*"'  ™  "i^"'  ~     i       Wl    T" 

-  /4^?/  enough  //?/  ^  //y?/>^  ^  />7tf 

FIG.  61.— Faulty  lines. 

The  Alphabet  of  Lines. 

As  the  basis  of  the  drawing  is  the  line,  a  set  of  conventional 
symbols  covering  all  the  lines  needed  for  different  purposes  may 
properly  be  called  an  alphabet  of  lines.  There  is  as  yet  no 
universally  adopted  standard,  but  the  following  set  is  adequate, 
and  represents  the  practice  of  a  majority  of  the  larger  concerns 
of  this  country. 

— — — — — — —  ( 1 )     Visible  outline . 

(2)     Invisible  outline. 

(3)  Center  line. 

(3a)  Center  line,  in  pencil. 

(4)  Dimension  line. 

(5)  Extension  line. 

(6)  Alternate  position. 

(7)  Line  of  motion. 

(8)  Cutting  plane. 


—  (9)     "Ditto"  or  repeat  line. 

(10)  Broken  material. 

(11)  Limiting  break. 


(12)  Cross-hatching  line. 


FIG.  62. — The  alphabet  of  lines. 


40 


ENGINEERING  DRAWING 


It  is  of  course  not  possible  to  set  an  absolute  standard  of  weight 
for  lines,  as  the  proper  size  to  use  will  vary  with  different  kinds 


FIG.  63.— The  alphabet  illustrated. 

and  sizes  of  drawings,  but  it  is  possible  to  maintain  a  given 
proportion. 

Visible  outlines  should  be  strong  full  lines,  at  least  one-sixty- 
fourth  of  an  inch  on  paper  drawings,  and  even  as  wide  as  one- 


FIG.  64.— The  alphabet  illustrated. 


thirty-second  of  an  inch  on  tracings.     The  other  lines  should 
contrast  with  this  line  in  about  the  proportion  of  Fig.  62. 

Dash  lines,  as  (2)  and  (7),  should  always  have  the  space  between 


THE  USE  OF  INSTRUMENTS 


41 


dashes  much  shorter  than  the  length  of  the  dash.     Figs.  63  and 
64  illustrate  the  use  of  the  alphabet  of  lines. 

The  Use  of  the  French  Curve. 

The  French  curve,  as  has  been  stated  on  page  14,  is  a  ruler  for 
non-circular  curves.  When  sufficient  points  have  been  deter- 
mined it  is  best  to  sketch  in  the  line  lightly  in  pencil  freehand, 
without  losing  the  points,  until  it  is  clean,  smooth,  continuous, 
and  satisfactory  to  the  eye.  The  curve  should  then  be  applied 
to  it,  selecting  a  part  that  will  fit  a  portion  of  the  line  most  nearly, 
and  noting  particularly  that  the  curve  is  so  laid  that  the  direction 
of  its  increase  in  curvature  is  in  the  direction  of  increasing  curv- 
ature of  the  line,  Fig.  65.  In  drawing  the  part  of  the  line  matched 


FIG.  65. — Use  of  the  curve. 

by  the  curve,  always  stop  a  little  short  of  the  distance  that  seems 
to  coincide.  After  drawing  this  portion  the  curve  is  shifted  to 
find  another  part  that  will  coincide  with  the  continuation  of  the 
line.  In  shifting  the  curve  care  should  be  taken  to  preserve  the 
smoothness  and  continuity  and  to  avoid  breaks  or  cusps.  This 
may  be  done  if  in  its  successive  positions  the  curve  is  always 
adjusted  so  that  it  conincides  for  a  little  distance  with  the  part 
already  drawn.  Thus  at  each  joint  the  tangents  must  coincide. 
If  the  curved  line  is  symmetrical  about  an  axis,  after  it  has 
been  matched  accurately  on  one  side,  marks  locating  the  axes 
may  be  made  in  pencil  on  the  curve  and  the  curve  reversed.  In 
such  a  case  exceptional  care  must  be  taken  to  avoid  a  "hump  "  at 
the  joint.  It  is  often  better  to  stop  a  line  short  of  the  axis  on 
each  side  and  to  close  the  gap  afterwards  with  another  setting  of 
the  curve. 


42 


ENGINEERING  DRAWING 


When  inking  with  the  curve  the  pen  should  be  held  perpen- 
dicularly and  the  blades  kept  parallel  to  the  edge.  Inking  curves 
will  be  found  to  be  excellent  practice. 

Sometimes,  particularly  at  sharp  turns,  a  combination  of 
circle  arcs  and  curve  may  be  used,  as  for  example  in  inking  an 
eccentric  ellipse,  the  sharp  curves  may  be  inked  by  selecting  a 
center  on  the  major  axis  by  trial,  and  drawing  as  much  of  an  arc 
as  will  practically  coincide  \vith  the  ends  of  the  ellipse,  then 
finishing  the  ellipse  with  the  curve. 

The  experienced  draftsman  will  sometimes  ink  a  curve  that 
cannot  be  matched  accurately,  by  varying  the  distance  of  the 
pen  point  from  the  ruling  edge  as  the  line  progresses,  but  the 
beginner  should  not  attempt  it. 

Exercises  in  the  Use  of  Instruments. 

The  twelve  following  figures  are  given  simply  as  a  typical  set 
of  progressive  exercises  for  practice  in  the  use  of  the  instruments. 
More  or  fewer  may  be  used  according  to  the  student's  evidence 
of  ability.  The  geometrical  figures  of  Chapter  IV  may  be  used 
for  the  same  purpose. 


FIG.  66. 


FIG.  67. 


FIG.  68. 


Lay  off  a  9"  x  12"  plate,  with  1/2"  border.     Divide  the  space 
inside  the  border  into  six  equal  parts,  with  the  dividers.     Locate 
the  center  of  each  space  by  drawing  short  intersecting  portions 
of  its  diagonals. 
Fig.  66.     An  Exercise  for  the  T-square,  Triangle  and  Scale. 

Through  the  center  of  the  space  draw  a  horizontal  and  a 
vertical  line,  measuring  on  these  lines  as  diameters  lay  off 
a  three-inch  square.  Along  the  lower  side  and  the  upper 
half  of  the  left  side  measure  3  / 8"  spaces  with  the  scale.  Draw 


THE  USE  OF  INSTRUMENTS 


43 


all  horizontal  lines  with  the  T-square  and  all  vertical  lines 
with  the  T-square  and  triangle. 

Fig.  67.  A  "Swastika."     For  T-square,  triangle  and  dividers. 
Draw  three-inch  square.     Divide  left  side  and  lower  side 
into  five  equal  parts  with  the  dividers.     Draw  horizontal 
and  vertical  lines  across  the  square  through  these  points. 
Erase  the  parts  not  needed. 

Fig.  68.  Converging  Lines.  Draw  three-inch  square.  Draw 
lines  AB,  BC,  DE  and  EF  at  30  degrees.  Divide  lower  side 
into  seven  equal  parts,  with  the  dividers.  Draw  the  vertical 
lines,  and  mark  divisions  on  AC  with  the  pencil  as  each  line 


FIG.  70. 


FIG.  71. 


is  drawn.  Through  the  division  points  on  top  and  bottom 
draw  the  converging  lines  using  the  triangle  alone  as  a 
straight-edge. 

Fig.  69.     A  Hexagonal  Figure.     For  30°-60°  triangle  and  bow 

points  (spacers). 

Through  the  center  of  the  space  draw  the  three  construction 
lines,  AB  vertical,  DE  and  FG  at  30  degrees.  Measure  CA 
and  CB  1  1/2"  long.  Draw  AE,  AF,  DB,  and  BG  at  30 
degrees.  Complete  hexagon  by  drawing  DF  and  GE 
vertical.  Set  spacers  to  3/32".  Step  off  3/32"  on  each  side 
of  the  center  lines,  and  3/16"  from  each  side  of  hexagon. 
Complete  figure  as  shown,  with  triangle  against  T-square. 

Fig.  70.  A  Street  Paving  Intersection.     For  45-degree  triangle  and 
scale. 

An  exercise  in  starting  and  stopping  short  lines.  Draw 
three-inch  square.  Draw  diagonals  with  45-degree  triangle. 
With  scale  lay  off  3/8"  spaces  along  the  diagonals,  from 


44 


ENGINEERING  DRAWING 


their  intersection.  With  45-degree  triangle  complete  figure, 
finishing  one-quarter  at  a  time. 

Fig.  71.  A    Maltese    Cross.     For    T-square,    spacers,    and  both 
triangles. 

Draw  three-inch  square  and  one-inch  square.  From  the 
corners  of  inner  square  draw  lines  to  outer  square  at  15 
degrees  and  75  degrees,  with  the  two  triangles  in  combina- 
tion. Mark  points  with  spacers  3/16"  inside  of  each  line  of 
this  outside  cross,  and  complete  figure  with  triangles  in 
combination. 


I 
\ 

\ 

\ 

\ 
\ 

\ 

\ 

\ 
\ 

\ 

\ 

\ 

i 

1 

y 

1 

1 

1 

1 

1 

1 

FIG.  72. 


FIG.  73. 


FIG.  74. 


Fig.  72.  Concentric  Circles.  For  compass  (legs  straight)  and 
scale. 

Draw  horizontal  line  through  center  of  space.  On  it  mark 
off  radii  for  six  concentric  circles  1/4"  apart.  In  drawing 
concentric  circles  always  draw  the  smallest  first.  The 
dotted  circles  are  drawn  in  pencil  with  long  dashes,  and 
inked  as  shown. 

Fig.  73.  Concentric  Arcs.     For  compass  (knuckle  joints  bent). 
On  horizontal  center  line  mark  off  eleven  points  I'/ 4"  apart, 
beginning  at  left  side  of  space.     Draw  horizontal  limiting 
lines  (in  pencil  only)  1  1/2"  above  and  below  center  line. 

Fig.  74.  Concentric  Arcs.     For  compass  and  lengthening  bar. 
On  horizontal  center  line  mark  off  eight  points  3/8"  apart, 
beginning  at  right  side  of  space     Center  of  arcs  is  center  of 
Fig.  72. 

Fig.  75.  Tangent  Arcs.  For  accuracy  with  compass  and  dividers. 
Draw  a  circle  three  inches  in  diameter.  Divide  the  circum- 
ference into  five  equal  parts  by  trial  with  dividers.  From 
these  points  draw  radial  lines  and  divide  each  into  four 


THE  USE  OF  INSTRUMENTS 


45 


equal  parts  with  spacers.  With  these  points  as  centers 
draw  the  semicircles  as  shown.  The  radial  lines  are  not  to 
be  inked. 

Fig.  76.  Tangent  Circles  and  Lines.     For  accuracy  with  compass 
and  triangles. 

On  base  A B,  31/2"  long  construct  an  equilateral  tri- 
angle, using  the  60-degree  triangle.  Bisect  the  angles 
with  the  30-degree  angle,  extending  the  bisectors  to  the 
opposite  sides.  With  these  middle  points  of  the  sides  as 
centers  and  radius  equal  to  1/2  the  side,  draw  arcs  cutting 
the  bisectors.  These  intersections  will  be  centers  for  the 


FIG.  75. 


FIG.  76. 


FIG.  77. 


inscribed  circles.  With  centers  on  the  intersection  of 
these  circles  and  the  bisectors,  round  off  the  points  of  the 
triangle  as  shown. 

Remember   the   rule  that  circles  are  inked  before  straight 
lines.     Construction  lines  are  not  to  be  inked. 
Fig.  77.  Tangents  to  Circle  Arcs.     For  bow  compasses. 

Draw  one  and  one-half  inch  square  about  center  of  space. 
Divide  AE  into  four  3/16"  spaces,  with  scale.  With  bow 
pencil  and  centers  A,  B,  C,  D  draw  four  semicircles  with 
3/8"  radius  and  so  on.  Complete  figure  by  drawing  the 
horizontal  and  vertical  tangents  as  shown. 


46  ENGINEERING  DRAWING 

A  PAGE  OF  CAUTIONS. 

Never  use  the  scale  as  a  ruler. 

Never  draw  with  the  lower  edge  of  the  T-square. 

Never  cut  paper  with  a  knife  and  the  edge  of  the  T-square  as  a 

guide. 

Never  use  the  T-square  as  a  hammer. 
Never  put  either  end  of  a  pencil  in  the  mouth. 
Never  jab  the  dividers  into  the  drawing  board. 
Never  oil  the  Joints  of  compasses. 
Never  use  the  dividers  as  reamers  or  pincers  or  picks. 
Never  take  dimensions  by  setting  the  dividers  on  the  scale. 
Never  lay  a  weight  on  the  T-square  to  hold  it  in  position. 
Never  use  a  blotter  on  inked  lines. 
Never  screw  the  nibs  of  the  pen  too  tight. 
Never  run  backward  over  a  line  either  with  pencil  or  pen. 
Never  leave  the  ink  bottle  uncorked. 
Never  hold  the  pen  over  the  drawing  while  filling. 
Never  dilute  ink  with  water.     If  too  thick  throw  it  away.     (Ink 

once  frozen  is  worthless  afterward.) 
Never  try  to  use  the  same  thumb  tack  holes  when  putting  paper 

down  a  second  time. 
Never  scrub  a  drawing  all  over  with  the  eraser  after  finishing. 

It  takes  the  life  out  of  the  inked  lines. 

Never  begin  work  without  wiping  off  table  and  instruments. 
Never  put  instruments  away  without   cleaning.     This   applies 

with  particular  force  to  pens. 
Never  put  bow  instruments  away  without  opening  to  relieve  the 

spring. 

Never  fold  a  drawing  '6r  tracing. 
Never  use  cheap  materials  of  any  kind. 


CHAPTER  IV. 

APPLIED  GEOMETRY. 

With  the  aid  of  a  straight-edge  and  compass  all  pure  geo- 
metrical problems  may  be  solved.  The  principles  of  geometry 
are  constantly  used  in  mechanical  drawing,  but  as  the  geometrical 
solution  of  problems  and  construction  of  figures  differs  in  ma-ny 
cases  from  the  draftsman's  method,  equipped  as  he  is  with 
instruments  for  gaining  time  and  accuracy,  such  problems  are 
not  included  here.  For  example,  there  are  several  geometrical 
methods  of  erecting  a  perpendicular  to  a  given  line,  in  his  ordinary 
practice  the  draftsman  equipped  with  T-square  and  triangles 
uses  none  of  them.  The  application  of  these  geometrical  methods 
might  be  necessary  occasionally  in  work  where  the  usual  drafting 
instruments  could  not  be  used,  as  for  example  in  laying  out  full 
size  sheet  metal  patterns  on  the  floor.  It  is  assumed  that 
students  using  this  book  are  familiar  with  the  elements  of  plane 
geometry  and  will  be  able  to  apply  their  knowledge.  If  a  par- 
ticular problem  is  not  remembered,  it  may  readily  be  referred  to 


in  any  of  the  standard  hand-books.  There  are  some  construc- 
tions however  with  which  the  draftsman  should  be  familiar  as 
they  will  occur  more  or  less  frequently  in  his  work.  The  few 
problems  in  this  chapter  are  given  on  this  account,  and  for  the 
excellent  practice  they  afford  in  the  accurate  use  of  instruments 
as  well. 

The  "trial  method"  of  dividing  a  line  was  explained  in  the 
previous  chapter.  A  convenient  geometrical  method  is  illus- 
trated in  Fig.  78.  To  divide  the  line  AB  into  (say)  five  equal 

47 


48 


ENGINEERING  DRAWING 


parts,  draw  any  line  AC  indefinitely,  6n  it  step  off  five  divisions 
of  convenient  length,  connect  the  last  point  with  B,  draw  lines 
through  the  points  parallel  to  CB  intersecting  A  B,  using  triangle 
and  straight-edge. 

To  transfer  a  given  polygon  ABCD  to  a  new  base  A'B',  Fig.  79. 
With  radii  AC  and  BC  describe  intersecting  arcs  from  centers 
A'B',  locating  the  point  C' '.  Similarly  with  radii  AD  and  BD 


FIG.  79. 

locate  the  point  D'.  Connect  BC  and  CD,  and  continue  the 
operation. 

To  inscribe  a  regular  octagon  in  a  given  square,  Fig.  80.  Draw 
the  diagonals  of  the  square.  With  the  corners  of  the  square  as 
centers  and  radius  of  half  the  diagonal  draw  arcs  intersecting 
the  sides  of  the  square  and  connect  these  points. 

To  draw  a  circular  arc  through  three  given  points  A,  B,  and  C, 


FIG.  ,80. 

Fig  81.  Join  AB  and  BC,  bisect  AB  and  BC  by  perpendiculars. 
Their  intersection  will  be  the  center  of  the  required  circle. 

To  draw  an  arc  of  a  given  radius  R  tangent  to  two  given  lines 
AB  and  CD,  Fig.  82.  Draw  lines  parallel  to  AB  and  CD  at 
distance  R  from  them.  The  intersection  of  these  lines  will  be 
the  center  of  the  required  arc. 

To  draw  a  reverse  or  "ogee"  curve  connecting  two  parallel 
lines  AB  and  CD,  Fig.  83.  Erect  perpendiculars  at  B  and  C. 


APPLIED  GEOMETRY ' 


49 


Any  arcs  tangent  to  the  lines  must  have  their  centers  on  these 
perpendiculars.  Join  B  and  C  by  a  straight  line.  Assume  point 
E  on  this  line  through  which  the  curve  is  desired  to  pass,  and 
bisect  BE  and  EC  by  perpendiculars.  Any  arc  to  pass  through 
B  and  E  must  have  its  center  on  a  perpendicular  at  the  middle 
point.  The  intersection  therefore  of  these  perpendiculars  with 
the  two  first  perpendiculars  will  be  the  centers  for  arcs  BE  and 


FIG.  83. 

EC.  This  line  might  be  the  center  line  for  a  curved  road  or  pipe. 
To  lay  off  on  a  straight  line  the  approximate  length  of  a  circle - 
arc,  Fig.  84.  Let  A  B  be  the  given  arc.  At  A  draw  the  tangent 
AD  and  chord  AB  produced.  Lay  off  AC  equal  to  half  the  chord 
AB.  With  center  C  and  radius  CB  draw  an  arc  intersecting  A% 
at  E,  then  AE  will  be  equal  in  length  be  to  the  arc  AB  (very 


FIG.  84. 

nearly).     If  the  given  arc  is  greater  than  60  degrees  it  should  be 
subdivided.* 

In  ordinary  work  the  usual  way  of  rectifying  an  arc  is  to  step 
around  it  with  the  dividers,  in  spaces  small  enough  as  practically 
to  coincide  with  the  arc,  and  to  step  off  the  same  number  on  the 
right  line,  as  in  Fig.  85. 

*  In  this  (Professor  Rankine's)  solution,  the  error  varies  as  the  fourth 
power  of  the  subtended  angle.     At  60  degrees  the  line  will  be  1/900  part 
short. 
4 


50 


ENGINEERING  DRAWING 


In  cutting  a  right  circular  cone  by  planes  at  different  angles 
four  curves  called  the  conic  sections  are  obtained,  Fig.  86.  These 
are  the  circle,  cut  by  a  plane  perpendicular  to  the  axis;  the  ellipse, 
cut  by  a  plane  making  a  greater  angle  with  the  axis  than  the 
elements  do;  the  parabola,  cut  by  a  plane  making  the  same  angle 
with  the  axis  as  the  elements  do;  the  hyperbola,  cut  by  a  plane 


FIG.  86. — The  conic  sections. 

making  a  smaller  angle  than  the  elements  do.  These  curves  are 
studied  mathematically  in  analytic  geometry  but  may  be  drawn 
without  a  knowledge  of  their  equations  by  knowing  something  of 
their  characteristics. 

As  an  ellipse  is  the  projection  of  a  circle  viewed  obliquely  it 
is  met  with  in  practice  oftener  than  the  other  conies,  aside  from 
the  circle,  and  draftsmen  should  be  able  to  construct  it  readily, 
hence  several  methods  are  given  for  its  construction,  both  as  a 
true  ellipse  and  as  an  approximate  curve  made  by  circle-arcs. 
In  the  great  majority  of  cases  when  this  curve  is  required  its 
long  and  short  diameters, i.e.,  its  major  and  minor  axes  are  known. 

Ellipse— First  Method. 

The  most  accurate  method  for  determining  points  on  the 
curve  is  shown  in  Fig.  87.  With  C  as  center  describe  circles  on 
the  two  diameters.  From  a  number  of  points  on  the  outer  circle 
as  P  and  Q  draw  radii  CP,  CQ,  etc.,  intersecting  the  inner  circle 
at  Pf,  Qf,  etc.  From  P  and  Q  draw  lines  parallel  to  CD,  and  from 
P'  and  Q'  lines  parallel  to  CB.  The  intersection  of  the  lines 
through  P  and  Pf  gives  one  point  on  the  ellipse.  The  intersection 
of  the  lines  through  Q  and  Q'  another  point,  and  so  on.  For 
accuracy  the  points  should  be  taken  closer  together  toward  the 
major  axis.  The  process  may  be  repeated  in  the  four  quadrants 
and  the  curve  sketched  in  lightly  freehand,  or  one  quadrant  only 


APPLIED  GEOMETRY 


51 


may  be  constructed  and  the  remaining  three  repeated  by  marking 
the  French  curve.  A  tangent  at  any  point  H  may  be  drawn  by 
projecting  the  point  to  the  outer  circle  at  K  and  drawing  the 
auxiliary  tangent  KL  cutting  the  major  axis  at  L.  From  L 
draw  the  required  tangent  LH. 


FIG.  88. 


Ellipse— Trammel  Method.     Fig.  88. 

On  the  straight  edge  of  a  strip  of  paper,  thin  cardboard  or 
sheet  celluloid  mark  the  distance  PQ  equal  to  one-half  the  major 
axis  and  PR  equal  to  one-half  the  minor  axis.  If  the  strip  be 
moved  keeping  Q  on  the  minor  axis  and  R  on  the  major  axis,  P 


FIG.  89. — An  Ellipsograph. 

will  give  points  on  the  ellipse.  This  method  will  be  found  very 
convenient,  as  no  construction  is  required,  but  for  accurate 
results  great  care  should  be  taken  to  keep  the  points  P  and  Q 
exactly  on  the  axes.  The  ellipsograph,  Fig.  89,  is  constructed 
on  the  principle  of  this  method. 


52 


ENGINEERING  DRAWING 


Ellipse — Pin  and  String  Method.     Fig.  90. 

This  well-known  method  sometimes  called  the  "gardener's 
ellipse"  is  often  used  for  large  work,  and  is  based  on  the  mathe- 
matical principle  of  the  ellipse  that  the  sum  of  the  distances 
from  any  point  on  the  curve  to  two  fixed  points  called  the  foci 
is  a  constant,  and  is  equal  to  the  major  axis.  The  foci  may  thus 
be  determined  by  making  DF  and  DF'  equal  to  AC.  Drive  pins 


FIG.  90. 

at  the  points  D,  F,  and  Ff  and  tie  an  inelastic  thread  or  cord 
tightly  around  the  three  pins.  If  the  pin  D  be  removed  and  a 
marking  point  moved  in  the  loop,  keeping  the  cord  taut,  it  will 
describe  a  true  ellipse.  The  bisector  of  the  angle  between  the 
focal  lines  will  be  normal  to  the  curve,  hence  a  tangent  at  any 
point  L  may  be  drawn  by  bisecting  the  exterior  angle  MLF. 


FIG.  91. 

Ellipse — Parallelogram  Method.    Fig.  91. 

This  method  may  be  used  with  either  the  major  -and  minor 
axes  or  with  any  pair  of  conjugate  diameters.  On 'the  diameters 
construct  the  parallelogram  ABDE.  Divide  AC  into  any  number 
of  equal  parts  and  AG  into  the  same  number  of  equal  parts, 
numbering  the  points  from  A.  Through  these  points  draw  lines 
from  D  and  E  as  shown.  Their  intersections  will  be  points  on 
the  curve. 


APPLIED  GEOMETRY 


53 


To  determine  the  major  and  minor  axes  of  an  ellipse,  the  conjugate 
axes  being  given.  The  property  of  conjugate  diameters  is  that 
each  is  parallel  to  the  tangent  to  the  curve  at  the  extremities  of 
the  other.  At  C  draw  a  semicircle  with  radius  CE.  Connect 
the  point  of  inte*rsection  P  of  this  circle  and  the  ellipse  with  D 
and  E.  The  major  and  minor  axes  will  be  parallel  to  the  chords 
DP  and  EP. 

Approximate  Ellipse  with  Four  Centers.     Fig.  92. 

Join  A  and  D.  Lay  off  DF  equal  to  AC -DC.  Bisect  AF  by 
a  perpendicular  crossing  AC  at  G  and  intersecting  DE  produced, 
at  H.  Make  CG'  equal  to  CG  and  CH'  equal  to  CE.  Then  Q, 


FIG.  93. 

G',  H,  and  H'  will  be  centers  for  four  arcs  approximating  the 
ellipse.  The  half  of  this  ellipse  when  used  in  masonry  construc- 
tion is  known  as  the  three-centered  arch. 

When  a  closer  approximation  is  desired,  the  five-centered  arch 
(eight-centered  ellipse)  may  be  constructed  as  in  Fig.  93.  Draw 
the  rectangle  AFDC,  connect  AD  and  draw  FH  perpendicular 
to  it.  Make  CM  equal  to  DL.  With  center  H  and  radius  HM 
draw  the  arc  MN.  With  A  as  center  and  radius  CL  intersect 
A  B  at  0.  With  P  as  center,  and  radius  PO  intersect  the  arc 
MN  at  N,  then  P,  N  and  H  are  centers  for  one-half  of  the 
semi-ellipse  or  "  five  centered  oval."  This  method  is  based  on 
the  principle  that  the  radius  of  curvature  at  the  end  of  the  minor 
axis  is  the  third  proportional  to  the  semi-minor  and  semi-major 
axes,  and  similarly  at  the  end  of  the  major  axis  is  the  third 
proportional  to  the  semi-major  and  semi-minor  axes.  The 
intermediate  radius  found  is  the  mean  proportional  between 
these  two  radii. 


54 


ENGINEERING  DRAWING 


Approximate  Ellipse.     Fig.  94. 

When  the  minor   axis  is  at  least  two-thirds  the  major,  the 
following  method  may  be  used: 

Make  CF  and  CG  equal  to  AB-DE. 

Make  CH  and  CI  equal  to  3/4  CF. 

F,  G,  H,  I  will  be  centers  for  arcs  E}  D,  A,  and  B. 


FIG.  95. — Curve  inked  with  circle  arcs. 


It  should  be  noted  that  an  ellipse  is  changing  its  radius  of 
curvature  at  every  point,  and  that  these  approximations  are 
not  ellipses  but  simply  curves  of  the  same  general  shape. 

Any  non-circular  curve  may  be  approxiamted  by  tangent 
circle  arcs,  selecting  a  center  by  trial,  drawing  as  much  of  an  arc 
as  will  practically  coincide  with  the  curve,  then  changing  the 
center  and  radius  for  the  next  portion,  remembering  always  that 


FIG.  96.— Parabola. 


FIG.  97.— Hyperbola. 


if  arcs  are  to  be  tangent,  their  centers  must  lie  on  the  common 
normal  at  the  point  of  tangency.  Many  draftsmen  prefer  to  ink 
curves  in  this  way  rather  than  to  use  irregular  curves.  Fig.  95 
illustrates  the  construction. 

A  parabola  may  be  drawn  in  a  manner  analogous  to  the  paral- 
lelogram method  of  the  ellipse,  as  shown  in  Fig.  96. 


APPLIED  GEOMETRY 


55 


One  of  the  commercial  uses  of  the  parabola  is  in  parabolic 
reflectors  and  search  lights. 

The  only  case  of  the  hyperbola  of  practical  interest  to  us  is 
the  equilateral  or  rectangular  hyperbola  on  its  asymptotes,  as 
representing  the. relation  between  the  pressure  and  volume  of 
steam  or  gas  expanding  under  the  law  pv  equals  c. 


FIG.  98. — Cycloid. 

To  draw  the  rectangular  hyperbola.     Fig.  97. 

Let  OA  and  OB  be  the  asymptotes  and  P  a  point  on  the  curve 
(this  might  be  the  point  of  cut  off  on  an  indicator  diagram). 
Draw  PC  and  PD.  Mark  any  points  on  PC;  through  these  points 
draw  ordinates  parallel  to  OA  and  through  the  same  points  lines 
to  0.  At  the  intersection  of  these  lines  with  PD  draw  abscissae. 
The  intersections  of  these  abscissae  with  the  ordinates  give  points 
on  the  curve. 


FIG.  99. — Epicycloid  and  hypocycloid. 

A  cycloid  is  the  curve  generated  by  the  motion  of  a  point  on 
the  circumference  of  a  circle  rolled  along  a  straight  line.  If  the 
circle  be  rolled  on  the  outside  of  another  circle  the  curve  is  called 
an  epicycloid;  when  rolled  inside  it  is  called  a  hypocycloid.  -  These 
curves  are  used  in  drawing  gear  teeth.  To  draw  a  cycloid,  Fig. 
98,  divide  the  rolling  circle  into  a  convenient  number  of  parts 
(say  12),  lay  off  the  rectified  length  of  the  circumference  with 
these  divisions  on  the  tangent  AB.  Draw  through  C  the  line  of 


56 


ENGINEERING  DRAWING 


centers  CD  and  project  the  division  points  up  to  this  line  by 
perpendiculars.  On  these  points  as  centers  draw  circles  repre- 
senting different  positions  of  the  rolling  circle,  and  project  across 
on  these  circles  in  order,  the  division  points  of  the  original  circle. 


FIG.  100. — Involute  of  a  pentagon. 


FIG.  101. — Involute  of  a  circle. 


These  intersections  will  be  points  on  the  curve.     The  epicycloid 

incl    .vj>  -'..ycloid  may  be  drawn  similarly  as  illustrated  in  Fig.  99. 

"v  :e  is  a  curve  generated  by  unwrapping  an  inflexible 

froiu  around  a  polygon.     Thus  the  involute  of  any  polygon 

may  be  drawn  by  extending  its  sides,  as  in  Fig.  100,  and  with  the 


FIG.  102. 


FIG.  103. 


corners  of  the  polygon  as  successive  centers  drawing  the  tangent 


arcs. 


A  circle  may  be  conceived  as  a  polygon  of  an  infinite  number  of 
sides.  Thus  to  draw  the  involute  of  a  circle,  Fig.  101,  divide  it 
into  a  convenient  number  of  parts,  draw  tangents  at  these  points, 


APPLIED  GEOMETRY  57 

lay  off  on  these  tangents  the  rectified  lengths  of  the  arcs  from  the 
point  of  tangency  to  the  starting  point,  and  connect  the  points 
by  a  smooth  curve.  It  is  evident  that  the  involute  of  a  circle 
is  the  limiting  case  of  the  epicycloid,  the  rolling  circle  becoming 
of  infinite  diameter.  It  is  the  basis  for  the  involute  system  of 
gearing. 

To  Draw  the  Spiral  of  Archimedes — making  one  turn  in  a  given 
circle,  Fig.  102. 

Divide  the  circumference  into  a  number  of  equal  parts,  drawing 
the  radii  and  numbering  the  points.  Divide  the  radius  N9-  1 
into  the  same  number  of  equal  parts,  numbering  from  the  center. 
With  C  as  center  draw  concentric  arcs  intersecting  the  radii  of 
corresponding  numbers,  and  draw  a  smooth  curve  through  these 
intersections.  This  is  the  curve  of 'the  heart  cam,  Fig.  103,  for 
converting  uniform  rotary  motion  into  uniform  reciprocal 
motion 


CHAPTER  V. 
LETTERING. 

To  give  all  the  information  necessary  for  the  complete  con- 
struction of  a  machine  or  structure,  there  must  be  added  to  the 
"graphical  language"  of  lines  describing  its  shape,  the  figured 
dimensions,  notes  on  materials  and  finish,  and  a  descriptive  title, 
all  of  which  must  be  lettered,  freehand,  in  a  style  that  is  perfectly 
legible,  uniform,  and  capable  of  rapid  execution.  So  far  as  its 
appearance  is  concerned  there  is  no  part  of  a  drawing  so  impor- 
tant as  the  lettering.  A  good  drawing  may  be  ruined  in  appear- 
ance by  lettering  done  ignorantly  or  carelessly. 

Lettering  is  not  mechanical  drawing.  The  persistent  use  by 
some  draftsmen  of  kinds  of  mechanical  caricatures  known  as 
geometrical  letters,  block  letters,  etc.,  made  up  of  straight  lines 
and  ruled  in  with  T-square  and  triangles,  is  to  be  condemned 
entirely.  Lettering  should  be  done  freehand,  in  a  style  suited 
to  the  class  of  the  drawing.*  On  working  drawings  the  lettering 
is  done  in  a  rapid  single-stroke  letter,  either  vertical  or  inclined, 
the  inclined  form  being  preferred.  The  ability  to  letter  well  in 
this  style  can  be  acquired  only  by  continued  and  careful  practice, 
but  it  can  be  acquired  by  any  one  with  normal  muscular  control 
of  his  fingers,  who  will  take  the  trouble  to  observe  carefully  the 
shapes  of  the  letters,  the  sequence  of  strokes  composing  them, 
and  the  rules  for  composition;  and  will  practice  faithfully  and 
intelligently.  It  is  not  a  matter  of  artistic  talent,  nor  even  of 
dexterity  in  handwriting.  Many  draftsmen  letter  well  who 
write  very  poorly. 

The  term  "  single-stroke  "  or  "  one-stroke  "  does  not  mean  that 
the  entire  letter  is  made  without  lifting  the  pen,  but  that  the 
width  of  the  stroke  of  the  pen  is  the  width  of  the  stem  of  the 
letter.  For  the  desired  height,  therefore,  a  pen  must  be  selected 

*  A  more  complete  study  of  the  subject  of  lettering  than  is  given  in  this 
chapter  is  necessary  for  draftsmen  who  will  have  any  variety  of  work, 
especially  civil  engineers  and  architects,  who  should  give  particular  atten- 
tion to  the  different  forms  of  Roman  letter.  Several  books  on  the  subject 
are  mentioned  in  Chapter  XV. 

58 


LETTERING  59 

which  will  give  the  necessary  width,  and  for  what  are  known  as 
"gothic"  letters  one  which  will  make  the  same  width  of  line 
when  drawn  horizontally,  obliquely,  or  vertically. 

The  coarse  pens  mentioned  on  page  13  are  particularly 
adapted  to  this  purpose.  Leonardt's  ball  point  506  F  will  make 
a  line  of  sufficient  width  for  letters  1/4"  high,  which  is  as  large  as 
would  be  used  on  any  ordinary  working  drawing.  516  EF  or 
Gillott's  1032  might  be  used  for  letters  3/16"  high  For  small 
letters  Hunt's  shot  point,  Gillott's  1050,  604  or  Spencerian  No.  1 
may  be  used.  Some  draftsmen  prepare  a  new  pen  by  dropping 
it  in  alcohol,  or  by  holding  it  in  a  match  flame  for  two  or  three 
seconds. 

Single -stroke  Vertical  Caps. 

The  upright  single-stroke  "  commercial  gothic"  letter  shown 
in  Fig.  104  is  a  standard  for  titles,  reference  letters,  etc.  In  the 
proportion  of  width  to  height  the  general  rule  is  that  the  smaller 
the  letters  the  more  extended  their  width  should  be.  A  low 
extended  letter  is  more  legible  than  a  high  compressed  one  and 
at  the  same  time  makes  a  better  appearance.  This  letter  is 

IHLFETNKMAV 

WXYZ4OOCGDUJP 

RBS83206957& 

FIG.  104. — Upright  single  stroke  capitals. 

seldom  used  in  compressed  form.  Before  commencing  the  prac- 
tice of  this  alphabet  some  time  should  be  spent  in  preliminary 
practice  to  gain  control  of  the  pen.  It  should  be  held  easily,  in 
the  position  illustrated  in  Fig.  105,  the  strokes  drawn  with  a 
steady,  even  motion  and  a  slight  uniform  pressure  on  the  paper, 
not  enough  to  spread  the  nibs  of  the  pen. 

For  the  first  practice  draw  in  pencil  top  and  bottom  guide 
lines  for.  3/16"  letters  and  with  a  516  F  or  similar  pen  make 
directly  in  ink  a  series  of  vertical  lines,  drawing  the  pen  down 
with  a  finger  movement.  This  one  stroke  must  be  practised 
until  the  beginner  can  get  lines  vertical  and  of  equal  weight. 
Remember  this  is  drawing,  not  writing,  and  that  all  the  flourish 


60 


ENGINEERING  DRAWING 


movements  of  the  penman  must  be  avoided.  It  may  be  found 
difficult  to  keep  the  lines  vertical;  if  so,  direction  lines  may  be 
drawn,  as  in  Fig.  105,  an  inch  or  so  apart  to  aid  the  eye. 


FIG.  105. — Position  for  lettering. 

It  is  ruinous  to  the  appearance  of  upright  letters  to  allow  them 
to  slant  forward.  A  slight  backward  slant  is  not  so  objectionable, 
but  the  aim  should  be  to  have  them  vertical.  When  this  stroke 

M 111^  —  —  /////  \\\\\ OOP 

FIG.  106.— Practice  strokes. 

has  been  mastered,  the  succeeding  strokes  of  Fig.  106  should  be 
taken  up.  These  strokes  are  the  elements  of  which  the  single 
stroke  letters  are  composed.  After  sufficient  practice  with  them, 


FIG.  107.—  Order  and  direction  of  strokes. 


they  should  be  combined  into  letters  in  the  order  of  Fig.  107, 
penciling  in  one  pattern  letter  and  numbering  its  strokes,  then 
drawing  directly  in  ink  several  beside  it.  Care  must  be  taken 


LETTERING  61 

to  keep  all  angles  and  intersections  clean  and  sharp.  Getting  too 
much  ink  on  the  pen  is  responsible  for  appearances  of  the  kind 
shown  in  Fig.  108. 

EHMNWTZ 

FIG.  108. — Too  much  ink. 

Single -stroke  Inclined  Caps. 

The  single  stroke  inclined  letter  made  to  a  slope  of  between 
60  and  70  degrees,  Fig.  109,  is  preferred  by  perhaps  a  majority  of 
draftsmen.  The  order  and  direction  of  strokes  for  the  capitals 
of  this  form  will  be  the  same  as  in  the  upright  form,  but  these 
letters  are  usually  not  extended.  If  a  rectangle  containing  a 

IHLFETNKMAV 

WX  YZ4  OQCGDUJP 

RBS83 2O6957& 

FIG.  109.— Inclined  capitals. 

flexible  O  should  be  inclined  the  curve  would  take  the  form 
illustrated  in  Fig.  110,  sharp  in  the  upper  right-hand  and  lower 
left-hand  corners,  and  stretched  flat  in  the  other  two  corners. 
This  characteristic  should  be  observed  in  all  curved  letters.  A 
convenient  and  pleasing  slope  for  these  letters  is  in  the  proportion 
of  2  to  5,  which  angle  may  be  made  by  laying  off  2  units  on  the 


horizontal  line  and  5  units  on  the  vertical  line.     Triangles  of 
about  this  angle  are  sold  by  the  dealers. 

The  first  requirement  is  to  learn  the  form  and  peculiarity  of 
each  of  the  letters.  Too  many  persons  think  that  lettering  is 
simply  printing  in  the  childish  way  learned  in  the  primary  grades. 
(Fig.  Ill  is  from  actual  examples  of  men's  work.)  There  is  an 
individuality  in  lettering  often  nearly  as  marked  as  in  handwrit- 


62  ENGINEERING  DRAWING 

ing,  but  it  must  be  based  on  a  careful  regard  for  the  fundamental 
letter  forms. 

In  our  practice  we  must  first  learn  the  individual  letters,  then 
compose  them  into  words  and  groups  of  words.  The  inclined 
letter  is  used  in  capitals  for  titles  and  headings,  and  in  capitals 


FIG.  111. — Inexcusable  faults. 

and  small  letters  for  less  important  captions,  and  for  notes  and 
descriptions.  In  all  lettering  there  should  always  be  drawn 
guide  lines  for  both  the  tops  and  bottoms.  In  the  inclined  style 
the  2  to  5  direction  lines  should  be  drawn  until  one  has  become 
very  proficient  in  keeping  the  lines  to  a  uniform  slant.  The  snap 
and  swing  of  professional  work  is  due  largely  to  two  things; 


FIG.  112. — Practice  strokes. 

keeping  the  letters  full,  and  close  together,  and  of  uniform  slope. 
The  beginner's  invariable  mistake  is  to  cramp  the  letters  and 
space  them  too  far  apart. 

It  will  be  noticed  that  the  letters  are  arranged  in  family  groups 
instead  of  in  the  usual  alphabetical  order.  After  practising  a 
few  preliminary  strokes  Fig.  112,  the  letters  should  be  taken  up 

r/ 


FIG.  113. — Order  and  direction  of  strokes. 


in  the  order  given  in  Fig.  113,  and  each  one  practised.  The  rule 
of  stability  requires  that  such  letters  as  B,  E,  K,  S,  X,  Z,  with 
the  figures  3  and  8  be  smaller  on  the  top  than  on  the  bottom,  and 
that  the  cross  lines  in  E,  F,  H,  be  slightly  above  the  middle. 
The  bridge  of  the  A  is  up  about  1/3  of  the  height.  Particular 


LETTERING 


63 


care  should  be  given  to  the  accurate  formation  of  numerals, 
making  them  round  and  full  bodied  and  of  the  same  heightf  as 
the  capitals. 

Single -stroke  Inclined  Lower  Case. 

The  lower  case  or  small  letters  of  this  style  are  drawn  with 
bodies   two-thirds   the   height   of   the   capitals.     This   letter   is 

/////-///    /.  /    / 


7 — T~7 — T 
FIG.  114.— Basis  of  Reinhardt  letter. 

generally  known  as  the  Reinhardt  letter,  in  honor  of  Mr.  Charles 
W.  Reinhardt,  Chief  of  the  Drafting  Department  of  the  "En- 
gineering News,"  who  has  used  it  so  successfully  in  the  illustra- 
tions for  that  periodical,  and  who  published'  it  as  a  system  in  his 
admirable  little  book  "  Lettering  for  Engineers."  It  is  the  minu- 
scule or  lower  case  letter  reduced  to  its  lowest  terms,  omitting  all 
unnecessary  hooks  and  appendages.  It  -  is  very  legible  and 


'      I      I 


FIG.   115.  —  Analysis  of  Reinhardt  letter. 

effective,  and  after  its  swing  has  been  mastered  can  be  made  very 
rapidly.  This  lower  case  letter  should  be  used  in  all  notes  and 
statements  on  drawings,  for  the  two  reasons  given  above,  it  is 
read  much  more  easily  than  all  capitals,  as  we  read  words  by  their 
shapes  and  are  familiar  with  these  shapes  in  the  lower  case  letters  ; 
and  it  can  be  done  fast. 


64  ENGINEERING  DRAWING 

All  the  letters  of  this  alphabet  are  based  on  two  strokes,  the 
straight  line,  and  the  partial  ellipse  whose  conjugate  axes  are 
the  slope  line  and  the  horizontal  line,  and  consequently  whose 
major  axis  is  about  45°,  Fig.  114.  The  general  direction  of 
strokes  is  always  downward  or  from  left  to  right,  and  in  the 
order  given  in  the  analyzed  letters  in  Fig.  115. 

In  the  composition  of  letters  into  words  three  general  rules 
must  be  remembered.  1,  Keep  the  letters  close  together;  2, 
have  the  areas  of  white  spaces,  the  back  grounds  between  the 
letters,  approximately  equal;  3,  keep  words  well  separated,  to  a 
space  at  least  equal  to  the  height  of  the  letter.  Paragraphs  are 
always  indented.  Fig.  116  is  an  example  of  spacing  of  letters, 
words,  and  lines. 

As  soon  as  the  letter  forms  have  been  mastered  all  the  practice 
should  be  directed  to  composition,  which  is  fully  as  important  as 
the  individual  shapes.  Titles  on  working  drawings  are  usually 
boxed  in  the  lower  right  hand  corner.  The  question  of  dimen- 
sioning and  the  contents  of  the  title  are  fully  discussed  in  Chapter 
IX  on  working  drawings. 

The  spac//70  ef  Setters  in  words,  fhe  spac/na 
of  words,  and  fhe  s/?ac//?a  0f//n0s  0se  a//  des/grt 
prop /ems  in  fhe  d/sjt?0s/f/0/?  ofwh/fe  0/xf  frfacfc. 
and  /he/r  success  ft//  so/vf/0/7  depends  or?  fhe 
artistic  perception  of  fhe  draffs/nan  more  fftar? 
on  ariyrc'/es  which  m/ghf  be  a/Ve/7. 

FIG.  116. — Composition. 


CHAPTER  VI. 
ORTHOGRAPHIC  PROJECTION. 

The  previous  chapters  have  been  preparatory  to  the  real  sub- 
ject of  engineering  drawing  as  a  language.  In  Chapter  I  was 
pointed  out  the  difference  between  the  representation  of  an  object 
by  the  artist  to  convey  certain  impressions  or  emotions,  and  the 
representation  by  the  engineer  to  convey  information. 

If  an  ordinary  object  be  looked  at  from  some  particular  station 
point,  one  may  usually  get  a  good  idea  of  its  shape,  because  (1) 
generally  more  than  one  side  is  seen,  (2)  the  light  and  shadow 
on  it  tell  something  of  its  configuration,  (3)  looked  at  with  both 


FIG.  117. — Perspective  projection. 

eyes  there  is  a  stereoscopic  effect  to  aid  in  judging  dimensions. 
In  technical  drawing  the  third  point  is  never  considered,  but  the 
object  is  drawn  as  if  seen  with  one  eye;  and  only  in  special  cases 
is  the  effect  of  light  and  shadow  rendered.  In  general  we  have 
to  do  with  outline  alone. 

If  a  transparent  plane  P,  Fig.  117,  be  imagined  as  set  up  between 
the  object  and  the  station  point  S  of  the  observer's  eye,  the 
5  65 


66 


ENGINEERING  DRAWING 


intersection  with  this  plane,  of  the  cone  of  rays  formed  by  lines 
from  the  eye  to  all  points  of  the  object,  will  give  a  picture  of  the 
object,  which  will  be  practically  the  same  as  the  picture  formed 
on  the  retina  of  the  eye  by  the  intersection  of  the  other  end 
(nappe)  of  the  cone. 

Drawing  made  on  this  principle  is  known  as  perspective  drawing 
and  is  the  basis  of  all  the  artist's  work.  In  a  technical  way  it  is 
used  chiefly  by  architects  in  making  preliminary  sketches  for 
their  own  use  in  studying  problems  in  design,  and  for  showing 
their  clients  the  finished  appearance  of  a  proposed  building.  It  is 
entirely  unsuited  for  working  drawings,  as  it  shows  the  object  as 
it  appears  and  not  as  it  really  is.  In  this  book  we  shall  take  up 


FIG.  118. — Orthographic  projection. 


FIG.   119.— The  H  plane. 


only  the  general  principles  of  perspective  as  applied  in  freehand 
sketching,  Chapter  X.  The  titles  of  several  books  which  ex- 
plain in  detail  the  methods  of  perspective  are  given  in  Chap- 
ter XV. 

Orthographic  Projection. 

The  problem  in  engineering  drawing  is  to  represent  accurately 
on  the  paper  having  only  two  dimensions,  length  and  breadth, 
the  three  dimensions  of  the  structure.* 

*  The  whole  subject  of  graphic  representation  of  solids  on  reference 
planes  comes  under  the  general  name  of  descriptive  geometry.  That  term, 
however,  has  by  common  acceptance  been  restricted  to  a  somewhat  more 
theoretical  treatment  of  the  subject  as  a  branch  of  mathematics.  This 
book  maybe  considered  as  an  ample  preparation  for  that  fascinating  subject, 
with  whose  aid  many  difficult  problem's  may  be  solved  graphically. 


ORTHOGRAPHIC  PROJECTION 


67 


If  the  station  point  S  be  conceived  as  moved  back  theoretically 
to  an  infinite  distance,  the  cone  of  rays  would  become  a  cylinder 
with  its  elements  perpendicular  to  the  picture  plane  7,  Fig. 
118,  and  its  intersection  with  it  will  give  a  picture  known  as  the 


\ 


FIG.  120.— The  H  plane  revolved. 


orthographic  projection.  If  we  then  discard  the  part  of  the  cylin- 
der between  the  picture  plane  and  the  eye  we  may  say  that  the 
orthographic  projection  of  an  object  on  a  plane  would  be  found 
by  dropping  perpendiculars  from  the  object  to  the  plane. 


FIG.   121. 


Evidently,  then,  a  line  or  surface  of  the  object  parallel  to  the 
plane  would  be  shown  in  its  true  size  (abed),  a  line  perpendicular 
would  be  projected  as  a  point  (ce)7  and  a  plane  surface  perpen- 
dicular to  the  picture  plane  would  be  projected  as  a  line 


68 


ENGINEERING  DRAWING 


(beef).     Thus  the  height  and  width  of  the  object  would  be 
shown  on  the  projection  in  their  true  size. 

If  now  another  plane  be  placed  horizontally  above  the  object 
and  perpendicular  to  the  first  plane,  Fig.  119,  the  projection  on 
this  plane  will  give  its  appearance  as  if  viewed  from  directly 
above,  showing  its  width  and  thickness.  If  this  plane  be  re- 
volved about  its  intersection  with  the  first  plane  until  they 


FIG.  122. — "The  transparent  box." 

coincide,  Fig.  120,  they  will  represent  the  plane  of  the  paper 
and  the  two  views  together  will  show  exactly  the  three  dimensions 
of  the  object.  Similarly  any  other  side  may  be  represented  by 
imagining  it  to  be  projected  to  a  plane  and  the  plane  afterward 
revolved  away  from  the  object  into  the  plane  of  the  paper. 

Thus  the  object,  Fig.  121,  may  be  thought  of  as  surrounded  by  a 
box  with  transparent  sides,  Fig.  122.  The  projections  on  these 
sides  would  be  practically  what  would  be  seen  by  looking  straight 
at  the  object  from  positions  directly  in  front,  above,  and  at  both 
sides.  These  " planes  of  projection"  when  revolved  into  one 
plane,  Fig.  123,  and  represented  on  the  paper  as  in  Fig.  124  give 
what  are  known  as  the  different  ''views"  of  the  object.  The 
projection  on  the  front  or  vertical  plane  is  known  as  the  front 


ORTHOGRAPHIC  PROJECTION 


69 


\ 


FIG.  123. — The  box  opened. 


5 

_,,    n 

nn  H  mi 

Coiil©'! 

FIG.  124. — The  three  projections. 


70 


ENGINEERING  DRAWING 


view,  vertical  projection,  or  front  elevation;  that  on  the  horizontal 
plane  as  the  top  view,  horizontal  projection,  or  plan;  that  on 
the  side  or  profile  plane  as  the  side  view,  profile  projection,  or 
side  elevation.  When  necessary  the  bottom  view  and  back 
view  may  be  made  in  a  similar  way,  by  projecting  to  their  planes 
and  opening  them  up  to  coincide  with  the  vertical  plane. 

Three  principles  are  evident,  first,  the  top  view  is  directly  over 
the  front  view,  second,  the  side  views  are  in  the  same  horizontal 
line  as  the  front  view,  third,  the  width  of  the  side  views  are  ex- 
actly the  same  as  the  width  of  the  top  view.  For  brevity  we 
shall  call  the  vertical  plane  V,  the  horizontal  plane  H  and  the 
profile  plane  P.  The  intersection  of  H  and  V  is  called  the  ground 
line,  GL,  and  the  intersections  of  P  with  H  and  V  called  the  H 
trace  of  P,  and  the  V  trace  of  P.  P  is  generally  revolved  about 
its  V  trace  as  in  the  illustration  in  Fig.  124,  but  may  be  revolved 
about  its  H  trace  as  in  Fig.  126.  Evidently  the  side  view  of  any 
point  as  Q  would  be  as  far  from  the  V  trace  of  P  as  its  top  view 
is  from  the  ground  line. 


FIG.  125. — First  angle  projection. 

Note.^  If  the  horizontal  and  vertical  planes  are  extended  beyond  their 
ntersection,  'four  dihedral  angles  will  be  formed,  which  are  numbered  as 
illustrated  in  Fig.  125.  If  the  object  be  placed  in  the  first  angle,  projected 
to  the  planes  and  the  planes  opened  as  before,  the  top  view  would  evidently 
fall  below  the  front  view,  and  if  the  profile  plane  were  added  the  view  of 
the  left  side  of  the  figure  would  be  to  the  right  of  the  front  view.  This 
system,  known  as  first  angle  projection,  was  formerly  in  universal  use,  but 
was  generally  abandoned  in  this  country  more  than  twenty  years  ago  and 
is  now  almost  obsolete.  The  student  should  understand  it,  however,  as  it 
may  be  encountered  occasionally  in  old  drawings,  in  some  book  illustrations, 
and  in  foreign  drawings.  In  England  some  attempt  is  being  made  to 
introduce  true  (third  angle)  projection,  but  as  yet  it  has  not  been  accepted 
to  any  extent. 


ORTHOGRAPHIC  PROJECTION 


71 


The  monument  Fig.  127  is  shown  in  orthographic  projection  in 
Fig.  128.  On  the  top  view  the  H  tr.  of  P  is  OA.  Evidently  in 
the  revolution  of  P  about  its  V  tr.?  the  H  tr.  would  revolve  to 
OB  and  the  points  projected  to  it  from  the  top  view  would  re- 
volve with  it.  These,  if  projected  down  from  OB  to  meet  hori- 


O 


FIG.  126. 


zontal  projectors  from  corresponding  points  on  the!  front  view, 
would  locate  the  points  on  the  side  view.  Fig.  129  illustrates  the 
principle  pictorially. 

In  practice  only  as  many  views  are  made  as  are  necessary  to 
describe  the  object,  and  the  ground  line  and  P  traces  are  not 


FIG.  127. 


FIG.  128. 


represented,  but  center  lines  or  other  lines  of  the  views  are  used 
for  reference  or  datum  lines  as  in  Fig.  130.  Thus  the  center 
line  of  the  side  view  may  be  regarded  as  the  edge  of  a  reference 
plane  whose  H  trace  is  the  center  line  on  the  top  view.  In  our 
theoretical  study  we  shall  make  the  three  views  of  a  number  of 


72 


ENGINEERING  DRAWING 


simple  objects,  at  first  working  from  the  GL  and  V  trace  of  P 
as  datum  lines,  afterward  using  center  lines;  developing  the 
ability  to  write  the  language,  and  exercising  the  imagination  in 
seeing  the  object  itself  in  space  by  reading  the  three  projections. 


FIG.  129. 


Fig.  131  shows  successive  cuts  made  on  a  block,  and  the  cor- 
responding projections  of  the  block  in  the  different  stages.  The 
effort  should  be  made  to  visualize  the  object  from  these  pro- 
jections until  the  projection  can  be  read  as  easily  as  the  picture. 
A  drawing  as  simple  as  A'  or  B'  can  be  read,  and  the  mental 


\ 

1 

f 

_] 

1 

1 

i 
i 

L, 

1 

1 

F 

EG.  130. 

picture  formed,  at  a  glance;  one  with  more  lines  as  E'  will  re- 
quire a  little  time  for  study  and  comparison  of  the  different 
views.  One  cannot  expect  to  read  a  whole  drawing  at  once  any 
more  than  he  would  think  of  reading  a  whole  page  of  print  at  a 
glance. 


ORTHOGRAPHIC  PROJECTION 


73 


Fig.  132  is  another  progressive  series,  illustrating  the  necessary 
use  of  hidden  lines. 

The  objects  in  Fig.  133  are  to  be  "written"  in  orthographic 


n 


C3H 

FIG..  131. 


projection   by   sketching  their  three   views.     Similar   practice 
may  be  gained  by  sketching  the  projections  of  any  simple  models, 


FIG.  132. 


or  objects  with  geometrical  outlines,  such  as  those  illustrated  in 
Fig.  390. 


FIG.   133. 


After  a  study  of  the  methods  of  pictorial  representation  (Chap- 
ter VIII)  we  shall  reverse  this  operation  and  practise  reading,  by 
making  the  pictures  of  objects  drawn  in  orthographic  projection. 


74 


ENGINEERING  DRAWING 


Auxiliary  Views. 

Sometimes  a  view  taken  from  another  direction  will  aid  in  show- 
ing the  shape  or  construction  of  an  object  to  better  advantage 
than  can  be  done  on  the  three  reference  planes  alone,  and  often 
such  a  view  may  save  making  one  or  more  of  the  regular  views. 
For  example,  the  three  views  of  Fig.  134  do  not  show  the  face  A 
clearly.  A  projection  on  a  plane  whose  edge  (H  trace)  is  S-S, 
parallel  to  the  face  A,  Fig.  135,  would  show  the  true  size  of  the 
face,  and  the  position  of  the  hole,  and  would  obviate  the  necessity 
for  a  side  view.  The  projection  is  imagined  as  made  by  dropping 
perpendiculars  to  the  plane,  and  revolving  the  plane  about  S-S 


0 

V*.. 

VL 

fe 

\J 

^^ 


1          1 

'l 

\J 

i 

i 

1  /~ 

FIG.  134. 


FIG.  135. — Auxiliary  projection. 


into  the  plane  of  the  top  view,  as  illustrated  pictorially  in  Fig. 
136.  Since  this  plane  is  perpendicular  to  H,  the  width  W  of 
this  view  would  evidently  be  the  same  as  the  width  of  the  front 
view. 

Such  a  plane  as  S  is  called  an  auxiliary  plane,  and  the  projec- 
tion on  it  an  auxiliary  projection  or  auxiliary  view. 

These  planes  may  be  set  up  anywhere  perpendicular  to  one  of 
the  planes  of  projection,  and  revolved  into  the  plane  of  the  paper. 
In  practical  work  extensive  use  is  made  of  auxiliary  views  in 
showing  the  true  size  of  sections  and  inclined  surfaces. 

The  plane  S  in  Fig.  136  was  taken  perpendicular  to  H  and  re- 
volved into  H.  It  might  as  readily  have  been  revolved  about 
its  V  trace  into  V.  Fig.  137  is  the  picture  of  an  object  with  the 
H  and  V  planes,  and  an  auxiliary  plane  parallel  to  one  of  the 


ORTHOGRAPHIC  PROJECTION 


75 


76 


ENGINEERING  DRAWING 


faces  of  the  object  and  perpendicular  to  V.  F.ig.  138  shows  the 
position  of  the  planes  and  the  projections  when  opened  up,  the 
auxiliary  plane  being  revolved  about  its  V  trace  to  coincide 


FIG.  138. — Auxiliary  projection. 


FIG.  139. — Auxiliary  projection. 


with  V.     These  figures  illustrate  clearly  that  the  dimensions  of 

the  auxiliary  view  are  obtainable  directly  from  the  other  views. 

In  practice  the  auxiliary  plane  trace  is  not  actually  drawn, 

but,  like  the  ground  line,  after  use  has  been  made  of  it  in  explain- 


FIG.  140. 


ing  the  principle,  its  position  is  simply  imagined,  and  the  views 
are  worked  from  center  lines.  Thus  in  Fig.  139  the  center  line 
on  the  auxiliary  view  is  really  the  projection  of  the  center  line 
of  the  top  view  or,  more  accurately,  the  edge  of  a  plane  whose  H 


ORTHOGRAPHIC  PROJECTION 


77 


trace  is  the  center  line  of  the  top  view,  and  the  perpendicular 
distance  of  any  point  as  p  or  q  from  the  center  line  on  the  top 
view  is  laid  off  perpendicular  to  the  center  line  on  the  auxiliary 
view. 

Often  it  is  not  necessary  to  project  the  whole  figure  on  the 
auxiliary  plane,  but  only  the  part  to  be  shown  in  true  shape,  as 
the  lug  or  pad  in  Fig.  140  or  the  cut  face  of  Fig.  141. 

An  auxiliary  plane  may  be  imagined  as  detached  from  its 
trace  and  may  be  set  off  anywhere  at  a  convenient  place  on  the 
paper. 


FIG.  141. 


FIG.  142.— Section  on  A-B. 


Sectional  Views. 

Often  it  is  not  possible  to  show  clearly  the  interior  construction 
or  arrangement  of  an  object  by  outside  views,  using  dotted  lines 
for  the  invisible  parts.  In  such  case  the  object  is  drawn  as  if  a 
part  of  it  were  cut  or  broken  away  and  removed.  A  projection 
of  this  kind  is  known  as  a  sectional  view,  or  section,  and  the  ex- 
posed cut  surface  of  the  material  is  indicated  by  "  section  lining." 
It  should  be  understood  that  in  thus  removing  an  obstructing 
portion  so  as  to  show  the  interior  on  one  view,  the  same  portion 
is  not  removed  from  the  other  views;  but  on  the  view  to  which 


78 


ENGINEERING  DRAWING 


the  cut  surface  is  perpendicular  the  trace  of  the  cutting  plane  is 
indicated  by  a  line.  Thus  in  Fig.  142  the  top  view  shows  the 
trace  of  the  cutting  plane  A-B,  and  the  front  view  is  a  section 


FIG.  143. 


showing  the  bearing  as  it  would  appear  if  the  part  in  front  of  the 
plane  A-B  were  removed.  Fig.  143  is  a  pictorial  illustration. 
This  figure  also  illustrates  the  fact  that  the  cutting  plane  need  not 


FIG.   144.— Half  section. 


be  continuous,  but  may  be  taken  so  as  to  show  the  construction 
to  the  best  advantage. 

When  a  figure  is  symmetrical  about  an  axis,  it  is  a  common 


ORTHOGRAPHIC  PROJECTION 


79 


practice  to  show  half  in  section  and  the  other  half  in  full.  Figs. 
144  and  145  are  examples.  Fig.  146,  an  illustration  of  a  broken 
section,  is  self-explanatory. 


FIG.  145.— Half  section. 


Little  auxiliary  views  known  as  turned  sections,  or  revolved 
sections,  are  of  great  convenience  in  showing  the  shape  of  some 
particular  part.  They  may  be  drawn  directly  on  the  view,  as 


FIG.   146. — Broken  section. 


in  Fig.  147,  or  the  piece  may  be  broken  to  admit  of  placing  the 
section,  as  in  Fig.  148. 

It   is   not   assumed   that   the   cutting  plane  cuts  everything 


FIG.  147. — Revolved  sections. 


through  which  it* passes.     It  is  a  practical  rule  in  drawing  that 
if  in  a  sectional  view  a  part  can  be  shown  more  clearly  by  leaving 


80 


ENGINEERING  DRAWING 


it  in  position  full,  it  is  so  left.  This  is  true  of  shafts,  bolts,  rods, 
keys,  etc.,  which  are  never  sectioned,  but  are  drawn  as  in  Figs. 
149  and  150.  A  combination  full  and  sectional  view,  known  as  a 
"dotted  section"  will  sometimes  show  the  construction  of  an 
object  economically.  Fig.  151  A  is  an  illustration. 


FIG.   148. — Revolved  section. 

Section  lining  is  done  with  a  fine  line,  generally  at  45  degrees, 
and  spaced  uniformly,  to  give  an  even  tint,  the  spacing  being 
governed  by  the  size  of  the  surface,  but  except  in  very  small 
drawings  not  less  than  1/16  of  an  inch.  On  drawings  to  be 
inked  or  traced  the  section  lining  is  only  indicated  freehand  in 


FIG.  149. 


FIG.  150. 


pencil,  and  is  done  directly  in  ink.  The  spacing  is  done  entirely 
by  the  eye.  Care  should  be  exercised  in  setting  the  pitch  by  the 
first  two  or  three  lines,  and  one  should  glance  back  at  the  first 
lines  often  in  order  that  the  pitch  may  not  gradually  change  to 
wider  or  narrower. 


ORTHOGRAPHIC  PROJECTION 


81 


Large  surfaces  in  section  are  sometimes  shown  as  in  Fig.  152. 
This  both  saves  time  and  improves  the  appearance.  Adjacent 
pieces  are  section  lined  in  opposite  directions,  and  are  often 


FIG.   151. — A  dotted  section. 


brought  out  more  clearly  by  varying  the  pitch,  using  lines  closer 
together  for  smaller  pieces. 

Different  materials  are  sometimes  indicated  by  conventional 
symbols.     The  use  of  those  symbols  is  discussed  in  Chapter  IX. 


FIG.   152. 


Revolution. 

The  natural  way  to  place  an  object  would  be  in  the  simplest 
position,  with  one  face  or  edge  parallel  to  a  plane  of  projection. 
6 


82 


ENGINEERING  DRAWING 


It  is  sometimes  necessary,  however,  to  represent  it  in  a  position 
oblique  to  the  planes.  In  such  a  case  it  may  be  necessary  to 
draw  the  object  first  in  a  simpler  position,  and  revolve  it  about  an 
axis  perpendicular  to  a  plane  of  projection  to  the  required 
position. 


FIG.  153. — Revolution  about  axis  perpendicular  to  H. 

Rule:  If  an  object  be  revolved  about  an  axis  perpendicular  to 
a  plane,  its  projection  on  that  plane  will  remain  unchanged  in 
size  and  shape,  and  the  dimensions  parallel  to  this  axis  on  other 
planes  will  be  unchanged. 

Thus  if  the  pyramid  Fig.  153  be  revolved  through  30  degrees  about 
an  axis  perpendicular  to  the  H  plane,  its  H  projection  will  take  the 


FIG.   154. — Revolution  about  axis  perpendicular  to  V. 

position  shown  at  B.  The  height  of  the  pyramid  has  not  been 
changed  in  the  revolution,  hence  the  front  and  side  views  are 
the  same  height  as  the  original  front  view.  If,  instead/ the  pyra- 
mid be  revolved  about  an  axis  perpendicular  to  V,  the  front  view 
will  be  unchanged  and  may  be  copied  in  the  new  position.  The 


ORTHOGRAPHIC  PROJECTION 


83 


distance  from  the  ground  line  to  any  point  in  the  top  view  would 
be  unchanged,  hence  the  new  top  view  may  be  found  by  pro- 
jecting up  from  the  front  view  and  across  from  the  original  top 
view,  Fig.  154. 

Similarly  in  the  revolution  forward  or  back,  about  an  axis 
perpendicular  to  P,  the  side  view  is  unchanged  and  the  dimensions 
(widths)  on  the  top  and  front  are  the  same  as  in  the  original 
position,  Fig.  155. 


FIG.  155. — Revolution  about  axis  perpendicular  to  P. 

Successive  revolutions  may  be  made  under  the  same  rules. 
Fig.  156  is  a  block  revolved  from  its  first  position  about  an  axis 
perpendicular  to  H  through  45  degees,  then  about  an  axis  per- 
pendicular to  P  through  45  degrees  until  the  cut  face  MNO  is 
parallel  to  the  vertical  plane.  To  avoid  confusion  it  is  well  to 
letter  or  number  the  corresponding  points  as  the  views  are  car- 
ried along. 

Evidently  the  only  difference  in  principle  between  revolutions 


84 


ENGINEERING  DRAWING 


and  auxiliary  planes  is  that  in  the  former  the  object  is  moved 
and  in  the  latter  the  plane  is  moved. 

Although  objects  in  practical  drawing  would  never  be  placed 
in  these  complicated  positions,  unless  unavoidable,  problems 
in  revolution  are  an  excellent  aid  in  the  understanding  of  the 
theory  of  projection. 


FIG.  156. — Successive  revolutions. 

The  True  Length  of  a  Line. 

These  principles  are  evident :  If  a  line  is  parallel  to  a  plane 
its  projection  on  that  plane  will  be  equal  in  length  to  the  line 
itself. 

If  a  line  is  perpendicular  to  a  plane  its  projection  on  the  plane 
will  be  a  point. 


ORTHOGRAPHIC  PROJECTION 


85 


If  a  line  is  inclined  to  a  plane  its  projection  will  be  shorter 
than  the  line. 

If  a  line  is  parallel  to  H  or  V  its  projection  on  the  other  plane 
will  be  parallel  to  the  ground  line. 

A  line  inclined  to  both  H  and  V  will  not  show  its  true  length 


FIG.  158. 


in  either  projection.  If  it  be  revolved  until  it  is  parallel  to  one 
of  the  planes  its  projection  on  that  plane  will  be  its  true  length. 
In  Fig.  157  the  line  AB  is  revolved  about  an  axis  perpendicular 
to  H  until  it  is  parallel  to  V  and  its  true  length  is  AvBvr. 
Fig.  158  is  a  similar  construction  with  the  axis  perpendicular  to  V. 


159. 


FIG.  160. 


Or  by  a  second  method  the  line  may  be  revolved  about  its 
projection,  into  the  plane.  This  is  illustrated  pictorially  in  Fig. 
159.  The  H  projection  of  the  line  AB  in  space  is  a  line  con- 
necting the  feet  of  all  the  perpendiculars  from  A  B  to  the  plane. 
These  perpendiculars  form  what  is  known  as  the  projecting  plane. 


86  ENGINEERING  DRAWING 

If  this  projecting  plane  be  revolved  about  its  H  trace,  which  is  the 
H  projection  of  the  line,  until  it  coincides  with  H,  the  line  will  be 
seen  in  its  true  length. 

Construction.  Fig.  160.  The  distance  of  A  and  B  below  H 
is  indicated  on  the  V  projection.  Thus  if  to  Ah  Bh  the  perpendic- 
ulars Ah  Ar  and  Bh  Br  be  drawn,  Ar  Br  will  be  the  true  length  of 
AB. 

Shade  Lines. 

In  the  alphabet  of  lines  the  visible  outline  was  indicated  as  a 
uniform,  bold,  full  line.  This  is  the  general  practice  for  working 
drawings. 

It  is  possible  by  using  two  weights  of  lines,  to  add  something 
to  the  clearness  and  legibility  of  a  drawing,  and  at  the  same 


FIG.   161. — Shading  a  circle. 

time  to  give  to  its  appearance  a  relief  and  finish  very  effective 
and  desirable  in  some  classes  of  work.  Shade  lines  are  required 
on  patent  office  drawings,  and  are  used  in  a  few  shops  on  assem- 
bly drawings,  but  for  ordinary  shop  drawings  the  advantage 
gained  is  overbalanced  by  the  increased  cost.  It  is  correct  to 
use  them  whenever  the  gain  in  legibility  and  appearance  is  of 
sufficient  importance  to  warrant  the  expenditure  of  the  added 
time  necessary. 

Theoretically  the  shade  line  system  is  based  on  the  principle 
that  the  object  is  illuminated  from  one  source  of  light  at  an  in- 
finite distance,  the  rays  coming  from  the  left  in  the  direction  of 
the  body  diagonal  of  a  cube,  so  that  the  two  projections  of  any 
ray  each  make  an  angle  of  45  degrees  with  the  GL.  Part  of  the 
object  would  thus  be  illuminated  and  part  in  shade,  and  a  shade 


ORTHOGRAPHIC  PROJECTION 


87 


line  is  a  line  separating  a  light  face  from  a  dark  face.  The  strict 
application  of  this  theory  would  involve  some  trouble,  and  it  is 
never  done  in  practice,  but  the  simple  rule  is  followed  of  shading 
the  lower  and  right  hand  lines  of  all  figures. 

The  light  lines  should  be  comparatively  fine  and  the  shade 
lines  about  three  times  their  width.  The  width  of  the  shade 
line  is  added  outside  the  surface  of  the  piece.  They  are  never 
drawn  in  pencil,  but  their  location  may  be  indicated,  if  desired, 
by  a  mark  on  the  line.  In  inking  a  shaded  drawing  all  light  lines 
alone  should  be  inked  first,  then  the  shade  lines. 


FIG.  162.— Shade  lines. 

A  circle  may  be  shaded  by  shifting  the  center  on  a  45-degree 
line  toward  the  lower  right  hand  corner,  to  an  amount  equal  to 
the  thickness  of  the  shade  line,  >and  drawing  another  semicircular 
arc  with  the  same  radius,  or  it  may  be  done  much  more  quickly, 
particularly  with  small  circles,  after  the  "knack"  has  been 
acquired,  by  keeping  the  needle  in  the  center  after  drawing  the 
circle  and  springing  the  compass  out  and  back  gradually  by 
pressing  with  the  middle  finger  in  the  position  of  Fig.  161. 
Never  shade  a  circle  arc  heavier  than  the  straight  lines. 

Fig.  162  is  an  example  of  a  shade  line  drawing.  The  aid  in 
reading  given  by  the  shade  lines  will  be  noted. 


88 


ENGINEERING  DRAWING 


Line  shading  is  a  method  of  representing  the  effect  of  light 
and  shade  by  ruled  lines,  used  on  patent  drawings,  "show  plans," 
drawings  for  illustration,  and  the  like-.  To  execute  it  effectively 


FIG.  163. 


FIG.  164. 


and 'rapidly  requires  practice  and  is  an  accomplishment  not 
usual  among  ordinary  draftsmen.  An  explanation  of  the 
methods,  a'nd  several  examples  illustrating  its  application  are 
given  in  Chapter  XIV,  page  259. 


FIG.  165. 


FIG.  166. 


PROBLEMS. 

If  drawn  to  the  dimensions  and  scales  given,  these  problems 
will  each  occupy  a  space  not  to  exceed  4"  x  5". 
Group  I. — Orthographic  from  pictorial  views. 
Prob.    1.  Draw  three  views  of  block,  Fig.  163,  using  G.L. 

2.  Draw  three  views  of  core  box,  Fig.  164,  using  center 
lines  (without  G.L.}. 


ORTHOGRAPHIC  PROJECTION 


89 


3.  Draw  three  views  of  box,  Fig.  165,  using  center  lines. 

4.  Draw  three  views  of  block,  Fig.  166,  using  G.L. 

5.  Draw  three  views  of  support,  Fig.  167,  using  center  lines. 

6.  Draw  three  views,  of  block,  Fig.  168,  using  G.L. 


FIG.  167. 


FIG.  168. 


7.  Draw  three  views  of  block,  Fig.  169,  using  G.L. 

8.  Draw  three  views  of  piece,  Fig.  170,  using  center  lines. 
When  three  views  are  specified,  the  top  view,  front 

view,  and  right  side  view  are  understood. 


FIG.  169. 


FIG.  170. 


Group  II. — Views  to  be  completed. 

Prob.    9.  Draw  the  top  and  front  views  given,  Fig.  171,  and  add 
side  view.     Scale  Q"  =  l  ft. 

10.  Draw  three  views  of  clamp,  Fig.  172.     Scale  6"  =  1  ft. 

11.  Complete  the  top  and  front  views  and  draw  side  view 
of  block,  Fig.  173..     Scale  3"  - 1  ft. 

12.  Draw  three  views  of  block,  Fig.  174.     Scale  3"  =  1  ft. 


90 


ENGINEERING  DRAWING 


FIG.  171. 


FIG.  172. 


*>!>        .1 

•FnJi 


T 

^ 


H% ' 
— j — i 
HT  'i 


Jl 


FIG.  173. 


FIG.   174. 


1 

pf-f 


W 


FIG.  175. 


FIG.  176. 


ORTHOGRAPHIC  PROJECTION 


91 


13.  Draw  three  views  of  circular  block,  Fig.  175.     Scale 
3"  =  1  ft. 

14.  Draw  three  views  of  block,  Fig.  176.     Scale  3"  =  1  ft. 
For  further  practice  the  bottom  and  left  side  views 

of  problems  12,  13,  and  14  may  be  drawn. 


FIG.  177. 


15.  Draw  front  view,  complete  top  view,  and  draw  left 
side  view  of  frame,  Fig.  177.     Scale  3"=^1  ft. 

16.  Draw  front  view,  top  view,  and  complete  left  side 
view  given,  of  the  standard,  Fig.  178.     Scale  6"  =  1  ft. 


FIG.  179. 


FIG.  180. 


Group  III. — Auxiliary  projections. 

Prob.    17.  Draw  the  front  view  given,  complete  the  top  view  and 

draw  auxiliary  view  on  the  given  C.L.  of  truncated 

pyramid,  Fig.  179.     Full  size. 
18.  Draw  auxiliary  view  of  cylinder,  Fig.  180. 


92 


ENGINEERING  DRAWING 


FIG.   181. 


FIG.  182. 


FIG.  183. 


ORTHOGRAPHIC  PROJECTION 


93 


19.  Draw  auxiliary  view  of  square  prism,  Fig.  181. 

20.  Draw  auxiliary  view  of  cylinder,  Fig.  182. 

21.  Draw  auxiliary  view  of  block,  Fig.  183. 


FIG.  184. 


22.  Draw  auxiliary  view  of  cone  cut  by  plane,  Fig.  184. 

23.  Draw  auxiliary  view  of  pentagonal  pyramid,  Fig.  185. 

24.  Draw  auxiliary  view  of  bearing,  Fig.  186.     Scale  3"  = 
1ft. 


FIG.  186. 

Group  IV. — Sectional  views. 

Prob.    25.  Draw  front  view  and  sectional  side  view  of  ring,  Fig. 

187.     Full  size. 
26.  Draw  front  view  and  sectional  top  view  of  eccentric, 

Fig.  188.     Scale  6"  =  1  ft. 


94 


ENGINEERING  DRAWING 


FIG.  188. 


FIG.  189. 


FIG.  191. 


ORTHOGRAPHIC  PROJECTION 


95 


27.  Draw  top  view  and  sectional  front  view  of  casting, 
Fig.  189.     Scale  6"  =  1  ft. 

28.  Draw  top  view,  side  view,  and  sectional  front  view  of 
body,  Fig.  190.     Scale  6"  =  1  ft. 


FIG.  193. 

Half  sections. 

29.  Draw  top  view  and  half-section  front  view  of  flanged 
piece,  Fig.  191.     Scale  3"  =  1  ft. 

30.  Draw  top  view  and  half-section  front  view  of  sleeve 
Fig.  192.     Scale  6"  =  1  ft. 


FIG.  194. 


31.  Draw  end  view  in  section,  and  front  view  with  lower 
half  in  section,  of  piston,  Fig.  193.     Scale  6"  =  1  ft. 

32.  Draw  top  view,  front  view  in  half -section,  and  end  view 
of  tool-rest  holder,  Fig.  194.     Scale  6"  =  1  ft. 


96 


ENGINEERING  DRAWING 


Group  V. — Revolution. 

Prob.   33.   (1)   Draw  three  views  of  Fig.  195  in  simplest  position, 
(2)   Revolve  from  position  (1)  about  an  axis  perpendic- 
ular to  H  through  15  degrees. 


FIG.  195. 


(3)  Revolve  from  position  (2)  about  an  axis  perpendic- 
ular to  V  through  45  degrees. 

(4)  Revolve  from  position  (1)  about  an  axis  perpendic- 
ular to  P  forward  through  30  degrees. 


r-^H  r-'f-*\ 

[HE!  VO 


o 

o 


5  6 

FIG.  195  A. 


(5)  Revolve  from  position  (2)  about  an  axis  perpendic- 
ular to  P  forward  through  30  degrees. 

(6)  Revolve  from  position  (3)  about  an  axis  perpendic- 
ular to  P  forward  through  30  degrees. 


FIG.  197. 


(4),  (5),  (6)  may  be  placed  to  advantage  under 
(1),  (2), and  (3)  so  that  the  widths  of  front  and  top 
views  may  be  projected  down  directly. 


ORTHOGRAPHIC  PROJECTION 


97 


In  problem  33  any  of  the  objects  in  Fig.  195  A 
may  be  used  instead  of  Fig.  195. 

34.  (1)  Draw  three  views  of  Fig.  196. 

(2)  Revolve  from  position  (1)  about  an  axis  perpendic- 
ular to  V  through  30  degrees. 

(3)  Revolve  from  position  (2)  about  an  axis  perpendic- 
ular to  H  through  45  degrees. 

35.  (1)  Draw  three  views  of  Fig.  197. 


1 

1  

H] 

1 


FIG.  198. 


(2)  Revolve  from  position  (1)  about  an  axis  perpendic- 
ular to  P  through  30  degrees. 

36.  Complete  top  and  front  views,  and  draw  side  view  of 
box  in  position  as  shown  in  Fig.  198,  using  auxiliary 
view  shown  at  A  to  obtain  projections  of  lid.  Scale 
6"  =  1ft. 

Group  VI. — True  length  of  lines. 

Prob.    37.  Find  true  length  of  the  body  diagonal  of  a  1  1/2"  cube. 

38.  Find  true  length  of  the  brace  AB  in  tower  diagram, 
Fig.  199. 

39.  Find  true  length  of  any  element,  as  A B,  of  oblique 
cone,  Fig.  200.     Scale  6"  =  1  ft. 

40.  Find  true  length  of  line  AB  of  pier,  Fig.  201.     Scale 
6"  =  1  ft. 

41.  Find  true  length  of  line  AB  on  brace,  Fig.  202.     Scale 
3/4"  =  1ft. 

7 


98 


ENGINEERING  DRAWING 


Group  VII. — Drawing  from  description. 

Prob.  42.  Draw  three  views  of  a  pentagonal  prism,  axis  V  long 
and  perpendicular  to  H,  circumscribing  circle  of  base 
1  1/8"  diam.,  surmounted  by  a  cylindrical  abacus 
(cap)  1  1/2"  diam.,  1/2"  thick. 


FIG.  199. 


FIG.  200. 


43.  Draw  three  views  of  a  triangular  card  each  edge  of 
which  is  1  3/4"  long.     One  edge  is  perpendicular  to  P, 
and  the  card  makes  an  angle  of  30  degrees  with  H. 

44.  Draw  three  views  of  a  circular  card  1  3/4"  diam.,  in- 


FIG.  201. 


FIG.  202. 


45. 


clined  30°  to  H,  and  perpendicular  to  V.  (Find  8 
points  on  the  curve). 

Draw  three  views  of  a  cylinder  1"  diam.,  2"  long,  with 
hexagonal  hole,  3/4"  long  diam.,  through  it.  Axis  of 
cylinder  parallel  to  H  and  inclined  30  degrees  to  V. 


ORTHOGRAPHIC  PROJECTION  99 

46.  Draw  top  and  front  views  of  a  hexagonal  plinth  whose 
faces  are  5/8"  square  and  two  of  which  are  parallel 
to  H,  pierced  by  a  square  prism  2  3/4"  long,  base  1/2" 
square.     The  axes  coincide,   are  parallel  to  H,  and 
make  an  angle  of  30  degrees  with  V.     The  middle 
point  of  the  axis  of  the  prism  is  at  the  center  of  the 
plinth. 

47.  Draw  the  two  projections  of  a  line  2"  long,  making  an 
angle  of  30  degrees  with  V,  and  whose  V  projection 
makes  45  degrees  with  G.L.,  the  line  sloping  down- 
ward and  backward  to  the  left. 

48.  Draw  three  views  of  a  square  pyramid  whose  faces  are 
isosceles  triangles  1  1/4"  base  and  2"  alt.,  lying  with 
one  face  horizontal,  the  H  projection  of  its  axis  at  an 
angle  of  30  degrees  with  G.L. 

49.  Draw  three  views  of  a  triangular  pyramid  formed  of 
four   equilateral   triangles   whose   sides   are    1    3/4". 
,The  base  makes  an  angle  of  45  degrees  with  H,  and 
one  of  the  edges  of  the  base  is  perpendicular  to  V. 

50.  Draw  top  and  front  views  of  a  rectangular  prism, 
base  5/8"  x  1  1/4"  whose  body  diagonal  is  13/4"  long. 
Find  projection  of  prism  on  an  auxiliary  plane  per- 
pendicular to  the  body  diagonal. 


CHAPTER  VII. 

DEVELOPED  SURFACES  AND  INTERSECTIONS.* 

A  surface  may  be  considered  as  generated  by  the  motion  of  a 
line.  Surfaces  may  thus  be  divided  into  two  general  classes,  (1) 
those  which  can  be  generated  by  a  moving  straight  line,  (2)  those 
which  can  be  generated  only  by  a  moving  curved  line.  The 
first  are  called  ruled  surfaces,  the  second,  double  curved  surfaces. 
Any  position  of  the  moving  line  is  called  an  element. 

Ruled  surfaces  may  be  divided  into  (a)  planes,  (b)  single  curved 
surfaces,  (c)  warped  surfaces. 

A  plane  may  be  generated  by  a  straight  line  moving  so  as  to 
touch  two  other  intersecting  or  parallel  straight  lines. 

Single  curved  surfaces  have  their  elements  either  parallel  or 
intersecting.  These  are  the  cylinder  and  the  cone;  and  a  third 
surface,  which  we  shall  not  consider,  known  as  the  convolute,  in 
which  the  consecutive  elements  intersect  two  and  two. 

Warped  surfaces  have  no  two  consecutive  elements  either 
parallel  or  intersecting.  There  is  a  great  variety  of  warped 
surfaces.  The  surface  of  a  screw  thread  and  of  the  pilot  of  a 
locomotive  are  two  examples. 

Double  curved  surfaces  are  generated  by  a  curved  line  moving 
according  to  some  law.  The  commonest  forms  are  surfaces  of 
revolution,  made  by  the  revolution  of  a  curve  about  an  axis  in 
the  same  plane,  as  the  sphere,  torus,  or  ring,  ellipsoid,  paraboloid, 
hyperboloid,  etc. 

In  some  kinds  of  construction  full  sized  patterns  of  different 
faces,  or  of  the  entire  surface  of  an  object  are  required;  as  for 
example  in  stone  cutting,  a  templet  or  pattern  giving  the  shape 
of  an  irregular  face,  or  in  sheet  metal  work,  a  pattern  to  which  a 
sheet  may  be  cut  that  when  rolled,  folded,  or  formed  will  make 
the  object. 

*  The  full  theoretical  discussion  of  surfaces,  their  classification,  proper- 
ties, intersections,  and  development  may  be  found  in  any  good  descriptive 
geometry. 

100 


DEVELOPED  SURFACES  AND  INTERSECTIONS  101 

The  operation  of  laying  out  the  complete  surface  on  one  plane 
is  called  the  development  of  the  surface. 

Surfaces  about  which  a  thin  sheet  of  flexible  material  (as  paper 
or  tin)  could  be  wrapped  smoothly  are  said  to  be  developable; 
these  would  include  figures  made  up  of  planes  and  single  curved 
surfaces  only.  Warped  and  double  curved  surfaces  are  non- 
developable,  and  when  patterns  are  required  for  their  construction 
they  can  be  made  only  by  some  method  of  approximation, 
which  assisted  by  the  pliability  of  the  material  will  give  the  re- 
quired form.  Thus,  while  a  ball  cannot  be  wrapped  smoothly,  a 
two-piece  pattern  developed  approximately  and  cut  from  leather 
may  be  stretched  and  sewed  on  in  a  smooth  cover,  or  a  flat  disc 
of  metal  may  be  die-stamped,  formed,  or  spun  to  a  hemispherical 
or  other  required  shape. 

We  have  learned  (page  74)  the  method  of  finding  the  true 
size  of  a  plane  surface  by  projecting  it  on  an  auxiliary  plane. 


FIG.  203.  FIG.  204. 

If  the  true. size  of  all  the  faces  of  an  object  made  of  planes  be 
found  and  joined  in  order,  at  their  common  edges,  the  result 
will  be  the  developed  surface.  This  may  be  done  usually  to  the 
best  advantage  by  finding  the  true  lengths  of  the  edges. 

The  development  of  a  right  cylinder  would  evidently  be  a 
rectangle  whose  width  would  be  the  altitude,  and  length  the 
rectified  circumference,  Fig.  203;  and  the  development  of  a 
right  cone  with  circular  base  would  be  a  sector  with  a  radius 
equal  to  the  slant  height,  and  arc  equal  in  length  to  the  circum- 
ference of  the  base,  Fig.  204. 

In  the  laying  out  of  real  sheet  metal  problems  an  allowance 
must  be  made  for  seams  and  lap,  and  in  heavy  sheets  for  the 
thickness  and  for  crowding  of  the  metal;  there  is  also  the  con- 
sideration of  the  commercial  sizes  of  material,  and  of  economy 
in  cutting,  in  all  of  which  some  practical  shop  knowledge  is 


102  ENGINEERING  DRAWING 

necessary.     In  this  chapter  we  will  be  confined  to  the  principles 

alone. 

In  the  development  of  any  object  we  must  first  have  its  pro- 
jections, drawing  only  such  views  or  parts  of  views  as  are  neces- 
sary to  give  the  lengths  of  elements  and  true  size  of  cut  surfaces. 

To  develop  the  hexagonal  prism,  Fig.  205. 

Since  the  base  is  perpendicular  to  the  axis  it  will  roll  out  into 
the  straight  line  AB.  This  line  is  called  by  sheet  metal  workers 
the  "stretchout."  Lay  off  on  AB  the  length  of  the  perimeter 
of  the  base,  and  at  the  points  1,  2,  3,  etc.,  erect  perpendiculars, 


FIG.  205. — Development  of  hexagonal  prism. 

called  "measuring  lines,"  representing  the  edges.  Measure  on 
each  of  these  its  length  as  given  on  the  front  view,  and  connect 
the  points.  Attach  to  one  of  the  top  lines  the  true  size  of  the 
cut  face  C,  and  to  one  of  the  bottom  lines  the  size  of  the  base. 
The  figure  will  then  be  the  development  of  the  entire  surface  of 
the  prism.  It  is  customary  to  make  the  seam  on  the  shortest 
edge. 

To  develop  the  cylinder,  Fig.  206. 

In  rolling  the  cylinder  out  on  a  tangent  plane  the  base,  being 
perpendicular  to  the  axis,  will  develop  into  a  straight  line. 
Divide  the  base,  here  shown  as  a  bottom  view,  into  a  number  of 
equal  parts,  representing  elements.  Project  these  elements  up 
to  the  front  view.  Draw  the  stretchout  and  measuring  lines  as 
before.  Transfer  the  lengths  of  the  elements  in  order,  either  by 


DEVELOPED  SURFACES  AND  INTERSECTIONS 


103 


projection  or  with  dividers,  and  connect  the  points  by  a  smooth 
curve.  This  might  be  one-half  of  a  two-piece  elbow.  Three- 
piece,  four-piece,  or  five-piece  elbows  may  be  drawn  similarly,  as 


FIG.  206. — Development  of  cylinder. 


FIG.  207. — Five-piece  elbow. 


illustrated  in  Fig.  207.  As  the  base  is  symmetrical,  one-half 
only  need  be  drawn.  In  these  cases  the  sections  as  B  will  de- 
velop on  their  center  lines  as  stretchouts,  and  measurements  will 


104 


ENGINEERING  DRAWING 


J_J_i£UJ 


FIG.  208. — Development  of  five-piece  elbow. 


FIG.  209. — Development  of  octagonal  dome. 


DEVELOPED  SURFACES  AND  INTERSECTIONS 


105 


be  taken  on  each  side  of  the  center  line,  since  the  center  line  repre- 
sents a  "right  section,"  i.e.  the  section  cut  by  a  plane  perpen- 
dicular to  the  axis. 

Evidently  any  elbow  could  be  cut  from  a  single  sheet  without 
waste  if  the  seams  were  made  alternately  on  the  long  and  short 
sides.  Fig.  208. 

The  development  of  the  octagonal  dome  Fig.  209  illustrates  an 
application  of  the  development  of  cylinders. 


FIG.  210. — Development  of  hexagonal  pyramid. 

To  develop  the  hexagonal  pyramid,  Fig.  210. 

The  edge  GA  is  shown  on  the  front  view  in  its  true  length.  As 
the  edges  are  all  of  equal  length,  an  arc  may  be  drawn  with  the 
radius  GA  and  the  perimeter  of  the  base  stepped  off  on  it.  The 
cutting  plane  intersects  the  edges  at  the  points  HJKL.  Revolve 
these  points  to  GA  to  find  the  true  length  of  the  intercepts  and 
measure  these  distances  on  the  corresponding  lines  of  the  develop- 
ment. Find  the  true  size  of  the  cut  face  and  attach  it  to  the 
development. 

The  rectangular  pyramid  Fig.  211  is  develped  in  a  similar  way, 
but  as  the  edge  EA  is  not  parallel  to  the  plane  of  projection  it 
must  be  revolved  to  EA'  to  obtain  its  true  length. 

To  develop  the  truncated  cone,  Fig.  212. 

Divide  the  base  into  a  convenient  number  of  equal  parts, 
project  these  points  on  the  front  view  and  draw  the  elements 


106 


ENGINEERING  DRAWING 


through  them.  With  a  radius  equal  to  the  slant  height  of  the 
cone,  i.e.  the  true  length  of  the  element  OA,  draw  an  arc  and  lay 
off  on  it  the  circumference  of  the  base;  draw  the  developed  posi- 


FIG.  211. — Development  of  rectangular  pyramid. 


FIG.  212.— Development  of  cone. 

tions  of  the  elements  and  on  them  measure  the  true  lengths 
from  the  vertex  to  the  cutting  plane,  found  by  revolving  each 
point  over  to  the  extreme  element  OA. 


DEVELOPED  SURFACES  AND  INTERSECTIONS 


107 


Double -curved  surfaces  are  developed  approximately  by 
assuming  them  to  be  made  up  of  parts  of  developable  surfaces. 
Thus  the  sphere  may  be  made  of  sections  of  cylinders  whose 


FIG.  213. — Sphere,  gore  method 


diameter  is  equal  to  the  diameter  of  the  sphere,  and  developed 
as  in  Fig.  213,  or  it  may  be  made  up  of  frustra  of  cones  and 
developed  as  in  Fig.  214. 


FIG.  214. — Sphere,  zone  method. 


Triangulation. 

The  commonest  and  best  method  for  approximate  develop- 
ment is  by  triangulation,  i.e.,  assuming  the  surface  to  be  made 
up  of  a  large  number  of  triangular  strips,  or  plane  triangles  with 


108 


ENGINEERING  DRAWING 


very  short  bases.  This  is  used  for  all  warped  surfaces,  and  for 
oblique  cones,  which,  although  single-curved  surfaces,  and  capable 
of  true  theoretical  development,  can  be  done  much  more  easily 
and  accurately  by  triangulation. 

The  method  is  extremely  simple.  It  consists  merely  in  divid- 
ing the  surface  into  triangles,  finding  the  true  lengths  of  the  sides 
of  each,  and  constructing  the  triangles  one  at  a  time,  joining 
them  on  their  common  sides.  A  study  of  Fig.  215,  the  develop- 
ment of  an  oblique  cone,  will  explain  the  method  completely. 


FIG.  215. — Development  of  oblique  cone  by  triangulation. 

In  this  case  the  triangles  all  have  a  common  vertex,  the  apex  of 
the  cone,  their  sides  are  elements,  and  their  bases  the  chords  of 
short  arcs  of  the  base  of  the  cone. 

Divide  the  base  into  a  number  of  equal  parts  1,  2,  3,  etc.  (as 
the  plan  is  symmetrical  about  the  axis  AhCh  one-half  only  need 
be  constructed).  If  the  seam  is  to  be  on  the  short  side,  the  line 
AC  will  be  the  center  line  of  the  development  and  may  be  drawn 
directly  at  A'C'  as  its  true  length  is  given.  Find  the  true  lengths 
of  the  elements  1A,  2A,  etc.,  by  revolving  them  until  parallel  to1 
V.  This  may  be  done  without  confusing  the  H  and  V  projections, 


DEVELOPED  SURFACES  AND  INTERSECTIONS 


109 


by  constructing  the  triangles  for  the  true  lengths  in  an  auxiliary 
figure  as  shown,  laying  off  the  lengths  of  the  H  projections  as 
bases  on  the  line  DC'  and  connecting  with  the  point  A" '.  With 
A'  as  center  and  radius  A'V  draw  an  arc  on  each  side  of  A'C'. 
With  C'  as  center  and  radius  Chl  intersect  these  arcs  at  1'. 
Then  A'V  will  be  the  developed  position  of  the  element  Al. 
With  1'  as  center  and  arc  1,  2,  intersect  A'2'  and  continue  the 
operation. 


FIG.  216. — Development  of  oblique  cone  by  triangulation. 

Fig.  216  is  an  oblique  cone  connecting  two  parallel  pipes  of 
different  diameters.  This  is  developed  in  the  same  way  as  Fig. 
215,  except  that  the  true  size  of  the  base  is  not  given  in  the  top 
view  and  must  be  revolved  until  parallel  to  H,  as  shown. 

Transition  Pieces. 

Transition  pieces  are  used  to  connect  pipes  or  openings  of 
different  shapes  of  cross-section.  Fig.  217,  for  connecting  a 
round  pipe  and  a  square  pipe  on  the  same  axis,  is  typical.  These 
are  always  developed  by  triangulation. 

The  piece  shown  in  Fig.  217  is  evidently  made  up  of  four 
isosceles  triangles  whose  bases  are  the  sides  of  the  square,  and 
four  parts  of  oblique  cones.  As  the  top  view  is  symmetrical 


110 


ENGINEERING  DRAWING 


about  both  center  lines,  one-fourth  only  need  be  divided.     The 
construction  is  illustrated  clearly  in  the  figure. 


FIG.  217. — Transition  piece. 


FIG.  218. — Transition  piece. 


Fig.  218  is  another  transition  piece  from  rectangular  to  round. 
By  using  the  turned  sections  of  one-half  the  round  opening,  the 
need  of  the  full  side  view  is  avoided. 


DEVELOPED  SURFACES  AND  INTERSECTIONS 


111 


The  Intersection  of  Surfaces.* 

The  habit  should  be  formed  of  thinking  of  surfaces  as  made  up 
of  elements,  the  successive  positions  of  the  generating  line. 
When  two  surfaces  intersect,  their  common  line,  the  line  of 
intersection,  would  be  found  by  connecting  the  points  at  which 
the  elements  of  one  surface  pierce  the  other. 

Two  reasons  make  it  necessary  for  the  draftsman  to  be  familiar 
with  the  methods  of  finding  the  intersections  of  surfaces,  first, 
intersections  are  constantly  occurring  on  working  drawings,  and 
must  be  represented,  second,  in  sheet  metal  combinations  the 
intersections  must  be  found  before  the  pieces  can  be  developed. 
In  the  first  case  it  is  only  necessary  to  find  a  few  points  usually, 
and  "guess  in"  the  curve;  in  the  second  case  enough  points 
must  be  determined  to  enable  the  development  to  be  laid  out 
accurately. 

Intersection  of  Two  Cylinders. 

Any  practical  problem  resolves  itself  into  some  combination  of 
the  geometrical  type  forms  of  solids. 

In  Fig.  219  the  intersection  of  two  cylinders  might  represent  a 
dome  on  a  boiler.  If  the  top  view  of  the  cylinder  A  is  divided 


LI 

I  i 

i  i 

< 

i  i 

•rjSs 
B 

41.  j 

FIG.  219. — Intersection  of  two  cylinders. 

into  a  number  of  equal  parts  the  points  will  represent  the  top 
views  of  elements.  Draw  the  side  views  of  these  elements,  which 
will  pierce  the  cylinder  B  as  shown.  If  these  points  be  projected 
across  to  meet  the  corresponding  elements  on  the  front  view  the 
intersections  will  be  points  on  the  curve.  Since  the  axes  inter- 

*  Often  called  "penetrations"  or  "interpenetrations." 


112 


ENGINEERING  DRAWING 


sect,  the  projection  of  the  invisible  part  of  the  curve  will  coincide 
with  the  visible  part. 

The  method  of  development  of  the  cylinder  A  is  evident  from 
the  figure. 

In  general,  the  method  of  finding  the  line  of  intersection  of  any 
two  surfaces  is  to  pass  a  series  of  planes  through  them  in  such  a 
way  as  to  cut  from  each  the  simplest  lines.  The  intersection  of 
these  lines  will  be  points  on  the  curve. 

In  Fig.  219  the  plane  T  may  be  assumed  as  cutting  out  two 
elements  from  the  cylinder  A  whose  intersections  with  the  ele- 
ment cut  from  the  cylinder  B,  being  points  common  to  both, 
cylinders,  will  be  points  on  the  curve,  as  shown  in  the  sketch. 


FIG.  220. — Two  cylinders,  axes  not  intersecting. 

This  principle  is  illustrated  in  Fig.  220  with  two  cylinders  whose 
axes  do  not  intersect.  If  the  cylinder  A  were  to  be  developed  a 
right  section  as  at  &-/S  would  have  to  be  taken,  whose  stretchout 
would  be  a  straight  line.  If  the  cutting  planes  were  taken  at 
uniform  distances  apart,  or  at  random,  the  elements  would  not 
be  spaced  uniformly  on  the  stretchout  but  would  be  found  as 
they  project  on  the  turned  section  of  $-/S. 

Intersection  of  Cylinder  and  Cone. 

To  find  the  intersection  of  a  cylinder  and  a  cone  the  cutting 
planes  may  be  taken  so  as  to  pass  through  the  vertex  of  the  cone 
and  parallel  to  the  elements  of  the  cylinder,  thus  cutting  ele- 
ments from  both  cylinder  and  cone;  or  with  a  right  cone  they  may 
be  taken  perpendicular  to  the  axes,  so  as  to  cut  circles  from  the 


DEVELOPED  SURFACES  AND  INTERSECTIONS 


113 


cone.  Both  these  methods  are  illustrated  in  Fig.  221.  Some 
judgment  is  necessary  in  the  selection  both  of  the  direction  and 
number  of  the  cutting  planes.  More  points  need  be  found  at  the 


FIG.  221. — Intersection  of  cylinder  and  cone. 

places  of  sudden  curvature  or  change  of  direction  of  the  line  of 
intersection. 

Cutting  spheres  instead  of  planes  may  be  used  to  advantage  in 
some  cases.     If  any  surface  of  revolution  be  cut  by  a  sphere  whose 


FIG.  222. 


FIG.  223. 


center  is  on  the  axis  of  revolution,  the  intersection  will  be  a 
circle.     This  principle  may  be  employed  in  finding  the  inter- 
section of  a  cylinder  and  cone  of  revolution,  whose  axes  intersect, 
8 


114 


ENGINEERING  DRAWING 


as  in  Fig.  222.  If  spheres  be  drawn  with,  center  at  the  intersec- 
tion of  the  axes  they  will  cut  circles  from  each,  whose  intersection 
will  be  points  on  the  curve. 

The  intersection  of  two  cones  of  revolution  may  be  found  in  the 
same  way,  Fig.  223.  The  cone  B  would  be  developed  by  cutting 
a  right  section  as  S-S  whose  stretchout  will  be  a  circle  arc,  locat- 
ing the  elements  on  it  and  finding  the  true  length  of  each  from 
the  vertex  to  the  line  of  intersection 


FIG.  224. — Intersection  of  a  surface  of  revolution  and  a  plane. 

It  is  often  necessary  on  a  drawing  to  represent  the  line  of  inter- 
section of  a  plane  and  a  surface  of  revolution,  such  as  is  shown 
in  Fig.  224.  The  method  is  clearly  illustrated  in  the  figure.  A 
series  of  planes  as  S-S  are  passed  perpendicular  to  the  axis  of 
revolution,  cutting  out  the  circles  shown  on  the  end  view.  The 
points  at  which  these  circles  cut  the  "flat"  are  projected  back 
as  points  on  the  curve. 

PROBLEMS. 

Selections  from  the  following  problems  may  be  constructed 
accurately  in  pencil,  without  inking.  Any  practical  problem  can 
be  resolved  into  some  combination  of  the  "type  solids,"  and  the 
exercises  given  illustrate  the  principles  involved  in  the  various 
combinations. 

When  time  permits,  an  added  interest  in  developments  may 


DEVELOPED  SURFACES  AND  INTERSECTIONS 


115 


be  found  by  working  the  problems  on  suitable  paper,  allowing  for 
lap,  and  cutting  them  out. 

In  the  sheet  metal  shops,  development  problems,  unless  very 
complicated,  are  usually  laid  out  directly  on  the  iron. 

Except  when  noted,  the  following  problems  may  be  drawn  in  a 
space  4"x5". 


Group  I. — Prisms,  Fig.  225. 

Prob.     1.  Develop  entire  surf  ace  of  triangu- 
lar prism  (A) 
2.  Develop  entire  surface  of  pentag- 
onal prism                                           (B) 


FIG.  226. 

3.  Develop  entire  surface  of  oblique 
square  prism  (C) 

4.  Develop  entire  surface  of  triangu- 
lar prism  (D) 


116  ENGINEERING  DRAWING 

Group  II.— Cylinders,  Fig.  226. 

Prob.  5.  Develop  entire  surface  of  cylinder  (A) 

6.  Develop  three-piece  elbow  (B) 

7.  Develop  one  section  of  octagonal 


FIG.  227. 


roof  and  find  true  shape  of  a  hip 
rafter  (C) 

8.  Develop  one  section  of  dome,  and 
find  true  shape  of  hip  (D) 


FIG.  228. 

Group  III. — Pyramids,  Fig.  227. 

Prob.     9.  Develop  entire  surface  of  triangu- 
lar pyramid  (A) 

10.  Develop    pattern    for    octagonal 
lamp  shade  (B) 

11.  Complete  top  view,  and  develop 
surface  of  pentagonal  pyramid       (C) 


DEVELOPED  SURFACES  AND  INTERSECTIONS 

12.  Complete  top  view  and  develop 
surface  of  oblique  hexagonal 
pyramid  (D) 

Group  IV. — Cones,  Fig.  228. 

Prob.  13.  Complete  top  view,  and  develop 

cone  (A) 

14.  Complete  top  view,  and  develop 
flange  and  hood  cones  of  (B) 

15.  Complete  top  view,  and  develop 
cone  (C) 

16.  Complete  top  view,  and  develop 
cone  (P) 


117 


FIG.  229. 


Group  V.— Triangulation,  Fig.  229  (space  5"x  8"). 

Prob.   17.  Develop  conical  connector  (A) 

18.  Develop  connnector  (B) 

19.  Develop  transition  piece  (C) 

20.  Develop  transition  piece  (D) 

21.  Develop  offset  boot  (E) 

22.  Develop  three-way  pipe  (F) 


118  ENGINEERING  DRAWING 

Group  VI. — Intersection  of  Prisms,  Fig.  230  (space  5"x  8") 
Prob.  23.  Find  the  line  of  intersection  of 

two  prisms  (A) 

24.  Find  the  line  of  intersection  of 
two  prisms  (B) 

25.  Find  the  line  of  intersection  of 
two  prisms  (C) 


26.  Find  the  line  of  intersection  of 

two  prisms  (D) 

Develop  the  surface  of  the  larger  prism  in  Probs.  23,  24,  25,  26. 

Group.  VII. — Intersection  of  Cylinders,  Fig.  231. 
Prob.  27.  Find  the  line  of  intersection  of 

two  cylinders  (A) 

28.  Find  the  line  of  intersection  of 
two  cylinders  (B) 


DEVELOPED  SURFACES  AND  INTERSECTIONS 

29.  Find  the  line  of  intersection  of 
two  cylinders  (C) 

30.  Find  the  line  of  intersection  of 
two  cylinders  (D) 


119 


FIG.  231. 

Group  VIII.— Intersection  of  Cylinder  and  Cone,  Fig.  232. 
Prob.  31.  Find  the  line  of  intersection  of 

cylinder  and  cone  (A) 

32.  Find  the  line  of  intersection  of 
cylinder  and  cone  (B) 

33.  Find  the  line  of  intersection  of 
cylinder  and  cone  (C) 

34.  Find  the  line  of  intersection  of 
cylinder  and  cone  (D) 

35.  Find  the  line  of  intersection  of 
cylinder  and  cone  (E) 

36.  Find  the  line  of  intersection  of 
cylinders  and  cone  (F) 


120 


ENGINEERING  DRAWING 


FIG    232. 


FIG.  233. 


DEVELOPED  SURFACES  AND  INTERSECTIONS 


121 


Group  IX. — Intersection  of  Two  Cones,  Fig.  233. 
Prob.  37.  Find  line  of  intersection  of  two 

cones  (A) 

38.  Find  line  of  intersection  of  two 

cones  (B) 

If  desired,  any  of  the  figures  in  Groups  VII,  VIII  and  IX  may 
be  developed,  in  a  space  4"  x  5". 


FIG.  234. 

Group  X. — Intersection  of  Surfaces  by  Planes,  Fig.  234, 
Prob.  39.  Find  line  of  intersection  of  (A) 

40.  Find  line  of  intersection  of  (B) 

41.  Find  line  of  intersection  of  (C) 

42.  Find  line  of  intersection  cut  by 
planes  R  and  S  from    cast-iron 
transition  piece  (D) 

43.  Find  line  of  intersection  cut  by 
planes  R  S  and  T  from  cast-iron 
transition  elbow  (E) 


CHAPTER  VIII. 
PICTORIAL  REPRESENTATION. 

We  have  noted  the  difference  between  perspective  drawing  and 
orthographic  projection.  Perspective  drawing  shows  the  object 
as  it  appears  to  the  eye,  but  its  lines  cannot  be  measured  directly. 
Orthographic  projection  shows  it  as  it  really  is  in  form  and 
dimensions,  but  to  represent  the  object  completely  we  have 
found  that  at  least  two  projections  were  necessary,  and  that  an 
effort  of  the  geometrical  imagination  was  required  to  visualize 
.it  from  these  views.  To  combine  the  pictorial  effect  of  perspec- 
tive drawing  with  the  possibility  of  measuring  the  principal 
lines  directly,  several  kinds  of  one  plane  projection  or  conven- 
tional picture  methods  have  been  devised,  in  which  the  third 
dimension  is  taken  care  of  by  turning  the  object  in  such  a  way 
that  three  of  its  faces  are  visible.  With  the  combined  advan- 
tages will  be  found  some  serious  disadvantages  which  limit  their 
usefulness.  They  are  distorted  until  the  appearance  is  often 
unreal  and  unpleasant;  only  certain  lines  can  be  measured;  the 
execution  requires  more  time,  particularly  if  curved  lines  occur, 
and  it  is  difficult  to  add  many  figured  dimensions,  but  with  all 
this,  the  knowledge  of  these  methods  is  extremely  desirable  and 
they  can  often  be  used  to  great  advantage.  Structural  details 
not  clear  in  orthographic  projection  may  be  drawn  pictorially, 
or  illustrated  by  supplementary  pictorial  views.  Technical 
illustrations,  patent  office  drawings  and  the  like  are  made 
advantageously  in  one  plane  projection;  layouts  and  piping  plans 
may  be  shown,  and  many  other  applications  will  occur  to  drafts- 
men who  can  use  these  methods  with  facility.  One  of  the  uses  to 
which  we  shall  apply  them  is  in  testing  the  ability  to  read^ortho- 
graphic  projections  bv  translating  into  pictorial  representation. 

Isometric  Drawing. 

The  simplest  of  these  systems  is  isometric  drawing. 
If  a  cube  in  orthographic  projection,  Fig.  235,  be  conceived  as 
revolved  about  a  vertical  axis  through  45  degrees,  then  tilted 

122  ' 


PICTORIAL  REPRESENTATION 


123 


forward  until  the  edge  AD  is  foreshortened  equally  with  A B  and 
AC,  the  front  view  in  this  position  is  said  to  be  in  isometric 
(equal  measure)  projection.  The  three  lines  A  B,  AC  and  AD 
make  equal  angles  with  each  other  and  are  called  the  isometric 
axes.  Since  parallel  lines  have  their  projections  parallel,  the 
other  edges  of  the  cube  will  be  respectively  parallel  to  these  axes. 
Any  line  parallel  to  an  isometric  axis  is  an  isometric  line,  and  the 
planes  of  these  axes  and  all  planes  parallel  to  them  are  called 
isometric  planes.  It  will  thus  be  noticed  that  any  line  or  plane 


FIG.  235. — Revolution  to  isometric  position. 

which  in  its  orthographic  projection  is  perpendicular  to  either  of 
the  reference  planes,  will  be  an  isometric  line  or  plane. 

In  this  isometric  projection  the  lines  have  been  foreshortened 
to  approximately  81/100  of  their  length  and  an  isometric  scale 
to  this  proportion  might  be  made  as  drawn  in  Fig.  236.  If  the 
amount  of  foreshortening  be  disregarded  and  the  full  lengths 
laid  off  on  the  axes,  a  figure  slightly  larger  but  of  exactly  the 
same  shape  would  result.  This  is  known  as  isometric  drawingt 
As  the  effect  of  increased  size  is  usually  of  no  consequence,  and 
the  advantage  of  measuring  the  lines  directly  with  an  ordinary 
scale  is  a  great  convenience,  isometric  drawing  is  used  almost 
exclusively  instead  of  isometric  projection. 

To  make  an  isometric  drawing  of  a  rectangular  object  start 
with  the  three  axes  120  degrees  apart,  drawing  one  vertical,  the 
other  two  with  the  30-degree  triangle.  Let  this  represent  the 
front  corner  of  the  object  and  measure  on  the  three  lines  its 
length,  breadth  and  thickness,  Fig.  237.  To  draw  intelligently  in 
isometric  it  is  only  necessary  to  remember  the  direction  of  the 
three  principal  isometric  planes.  Hidden  lines  are  always 
omitted  except  when  necessary  for  the  description  of  the  piece. 


124 


ENGINEERING  DRAWING 


Lines  not  parallel  to  one  of  the  isometric  axes  are  called  non- 
isometric  lines.  The  first  rule  is,  measurements  can  be  made  only 
on  isometric  lines;  and  conversely,  measurements  cannot  be  made 
on  non-isometric  lines.  Thus  the  diagonals  of  the  face  of  the 
cube,  Fig.  235,  are  non-isometric  lines,  and  although  equal  in 


FIG.  236. — An  isometric  scale. 


FIG.  237. — The  isometric  axes. 


length,  are  evidently  of  very  unequal  length  on  the  isometric 
drawing. 

To  draw  an  object  composed  of  non-isometric  lines,  an  iso- 
metric construction  must  be  built  up  and  the  points  located  by 


FIG.  238. — Isometric  construction  lines. 


isometric  coordinates.  Thus  the  hexagonal  prism,  Fig.  238, 
may  be  enclosed  in  the  rectangular  box  and  the  corners  located 
on  these  isometric  lines  by  measuring  the  orthographic  projection. 
It  is  not  at  all  necessary  actually  to  enclose  the  object  in  rec- 
tangular construction.  In  many  instances  it  is  better  to  get  the 


PICTORIAL  REPRESENTATION 


125 


isometric  coordinates  by  offsets.     Figs.  239    and   240  are  self- 
explanatory. 

Of  course  angles  in  isometric  drawing  cannot  be  measured  in 
degrees.  In  general  to  represent  any  angles,  or  combination  of 
non-isometric  lines,  their  orthographic  view  must  be  drawn  first, 


FIG.  239. — Offset  construction. 

adding  construction  lines  which  can  be  drawn  isometrically,  and 
transferring  the  measurements  from  the  orthographic  to  these 
isometric  lines. 

A  circle  on  any  isometric  plane  would  be  projected  as  an 
ellipse.  It  may  be  constructed  from  the  orthographic  projection 
by  coordinates,  or  by  the  method  of  conjugate  diameters.  A 


FIG.  240. — Offset  construction. 

four-centered  circle-arc  approximation  sufficiently  accurate  for 
all  ordinary  work  is  made  by  drawing  a  perpendicular  from  the 
point  of  tangency,  that  is,  the  middle  point  of  each  side  of  the 
square.  As  the  center  of  any  arc  tangent  to  the  line  at  this  point 
must  lie  on  the  perpendicular,  the  intersections  of  these  perpen- 


126 


ENGINEERING  DRAWING 


diculars  would  be  centers  for  arcs  tangent  to  two  sides,  Fig.  241. 
Two  of  these  intersections  will  evidently  fall  in  the  corners  of  the 
square,  as  the  lines  are  altitudes  of  equilateral  triangles.  The 
construction  of  Fig.  241  may  thus  be  made  by  simply  drawing 


FIG.  241. — Approximate  isometric  circle. 

60-degree  lines  from  the  corners  A  and  B.  To  draw  any  circle- 
arc,  the  isometric  square  of  its  diameter  should  be  drawn  in  the 
plane  of  the  face,  with  as  much  of  this  construction  as  is  necessary 
to  find  centers  for  the  part  of  the  circle  needed.  Fig.  242  shows 
arcs  on  the  three  visible  faces  with  the  construction  indicated. 


FIG.  242. — Construction  of  isometric  circles. 


If  a  true  ellipse  be  plotted  in  the  same  square  as  this  four- 
centered  approximation  it  will  be  a  little  longer  and  narrower, 
and  of  more  pleasing  shape,  but  in  the  great  majority  of  drawings 
the  difference  is  not  sufficient  to  warrant  the  extra  expenditure 


PICTORIAL  REPRESENTATION 


127 


of  time  required  in  execution.  The  construction  of  a  closer 
approximation  with  eight  centers  as  illustrated  in  Fig.  243.  This 
might  be  used  when  a  more  accurate  drawing  of  an  inscribed 
circle  is  required. 

It  is  evident  that  the  isometric  drawing  of   a  sphere  would 


FIG.  243. 


FIG.  244. — Reversed  axes. 


have  a  diameter  equal  to  the  long  axis  of  the  ellipse  inscribed  in 
the  isometric  square  of  the  real  diameter  of  the  sphere,  as  this 
ellipse  would  be  the  isometric  of  a  great  circle  of  the  sphere. 

It  is  often  desirable  to  show  the  lower  face  of  an  object  by 
tilting  it  back  instead  of  forward,  thus  reversing  the  axes  to  the 


FIG.  245. — Construction  with  reversed  axes. 

position  of  Fig.  244.  The  construction  is  just  the  same  but  the 
direction  of  the  principal  isometric  planes  must  be  remembered. 
Figs.  245  and  246  are  applications.  Sometimes  a  piece  may  be 
shown  to  better  advantage  with  the  main  axis  horizontal  as  in 
Fig.  247. 


128 


ENGINEERING  DRAWING 


FIG.  246. — Architectural  detail  on  reversed  axes. 


FIG.  247. — Main  axis  horizontal. 


FIG.  248. — Isometric  section. 


FIG.  249. — Isometric  half  section. 


PICTORIAL  REPRESENTATION 


129 


The  isometric  section  and  half  section  may  sometimes  be 
employed  to  good  advantage.  The  cutting  planes  are  taken  as 
isometric  planes,  and  the  section  lining  done  in  a  direction  to  give 
the  best  effect.  Figs.  248  and  249  are  examples. 

Shade  lines  in  isometric  drawings  have  no  value  so  far  as  aiding 
in  the  reading  is  concerned,  but  they  may  by  their  contrast  add 


FIG.  250. 


FIG.  251. 


some  attractiveness  to  the  appearance.  Assuming  the  light  as 
coming  from  the  left  in  the  direction  of  body  diagonal  of  a  cube, 
and  disregarding  shadows,  shade  lines  separating  light  from  dark 
faces  would  be  added  as  in  Fig.  250. 

Another  method  popular  among  patent  draftsmen  and  others 
using  this  kind  of  drawing  for  illustration,  is  to  bring  out  the 
nearest  corner  with  heavy  lines,  as  Fig.  251. 


FIG.  252. — Illustration  of  first  rule. 

Oblique  projection,  sometimes  called  cavalier  projection,  is 
based  on  the  theoretical  principle  that  with  one  face  of  the  object 
parallel  to  the  picture  plane,  if  the  projectors  instead  of  being 
perpendicular  to  it  as  in  orthographic  and  isometric,  make  an 
angle  of  45  degrees  with  it  in  any  direction,  lines  perpendicular 
9 


130 


ENGINEERING  DRAWING 


to  the  plane  would  be  projected  in  their  true  length.  It  ,would 
thus  be  similar  to  isometric  in  having  three  axes,  representing 
three  mutually  perpendicular  lines,  upon  which  measurements 
could  be  made.  Two  of  th£  axes  would  always  be  at  right  angles 
to  each  other,  being  in  the  plane  parallel  to  the  picture  plane, 


FIG.  253. — Illustration  of  second  rule. 


and  the  cross  axis  might  be  at  any  angle,  30  degrees  being  gener- 
ally used.  Thus  any  face  parallel  to  the  picture  plane  will  be 
projected  without  distortion,  an  advantage  over  isometric  of 
particular  value  in  the  representation  of  objects  with  circular  or 


FIG.  254.— (A)  not  (B). 


irregular  outline,  and  the  first  rule  for  oblique  projection  would 
be,  place  the  object  with  the  irregular  outline  or  contour  parallel 
to  the  picture  plane.  Fig.  252  A  instead  of  B  or  C. 

One  of  the  greatest  disadvantages  in  the  use  of  either  isometric 
or  oblique  drawing  is»the  effect  of  distortion  produced  by  the  lack 


PICTORIAL  REPRESENTATION 


131 


of  convergence  in  the  receding  lines,  the  violation  of  perspective. 
This  in  some  cases,  particularly  with  large  objects,  becomes  so 
painful  as  practically  to  prohibit  the  use  of  these  methods.  It 
is  perhaps  even  more  noticeable  in  oblique  than  in  isometric, 
and  of  course  increases  with  the  length  of  the  cross  axis.  Hence 


FIG.  255. 

the  second  rule,  always  have  the  longest  dimension  parallel  to 
the  picture  plane.     A  not  B  in  Fig.  253. 

In  case  of  conflict  between  these  two  rules  the  first  should 
have  precedence,  as  the  advantage  of  having  the  irregular  face 
without  distortion  is  greater  than  is  gained  by  the  second  rule. 
Fig.  254. 


FIG.  256. — Offsets  from  right  section. 

It  will  be  noted  that  so  long  as  the  front  of  the  object  is  in  one 
plane  parallel  to  the  plane  of  projection,  the  front  face  of  the 
oblique  projection  is  exactly  the  same  as  the  orthographic. 
When  the  front  is  made  up  of  more  than  one  plane,  particular 
care  must  be  exercised  in  preserving  the  relationship  by  selecting 
one  as  the  starting  plane  and  working  from  it.  In  such  a  figure 
as  the  link,  Fig.  255,  the  front  bosses  may  be  imagined  as  cut  off 


132 


ENGINEERING  DRAWING 


on  the  plane  A-A,  and  the  front  view,  i.e.,  the  section  on  A-A 
drawn  as  the  front  of  the  oblique  projection.  On  axes  through 
the  centers  C  and  D  the  distances  CE  behind  and  CF  in  front  may 
be  laid  off.  When  an  object  has  no  face  perpendicular  to  its 


FIG.  257. — Piping  system  in  oblique  drawing. 

base  it  may  be  drawn  in  a  similar  way  by  cutting  a  right  section 
and  measuring  offsets  from  it  as  in  Fig.  256. 

This  offset  method,  previously  illustrated  in  the  isometric 
drawings,  Figs.  239  and  240,  will  be  found  to  be  a  most  rapid  and 
convenient  way  for  drawing  almost  any  figure,  and  it  should  be 
studied  carefully. 


FIG.  258. — Circle  construction. 


FIG.  259.— "Cabinet"  drawing. 


Fig.  257  is  an  illustration  of  a  piping  lay-out,  showing  the  value 
of  oblique  drawing  in  explaining  clearly  what  would  be  very 
difficult  to  represent  in  orthographic. 

Circles  in  oblique  drawing  may  either  be  plotted,  or  may  be 
drawn  approximately,  on  the  same  principle  as  Fig.  241,  by 
erecting  perpendiculars  at  the  middle  points  of  the  containing 
square.  In  isometric  it  happens  that  one  intersection  falls  in 


PICTORIAL  REPRESENTATION 


133 


the  corner  of  the  square,  and  advantage  is  taken  of  the  fact. 
In  oblique  its  position  depends  on  the  angle  of  the  cross  axis. 
Fig.  258  shows  three  oblique  squares  at  different  angles  and  their 
inscribed  circles. 

Cabinet  drawing  is  a  modification  of  oblique  projection  in 
which  all  the  measurements  parallel  to  the  cross  axis  are  reduced 
one-half,  in  an  attempt  to  overcome  the  appearance  of  excessive 
thickness  produced  in  oblique  drawing.  The  cabinet  drawing 
Fig.  259  may  be  compared  with  the  oblique  drawing  Fig.  255. 

Axonometric  Projection. 

The  principle  of  isometric  projection  was  shown  in  the  double 
revolution  of  the  cube.  A  cube  might  be  revolved  into  any 
position  showing  three  of  its  faces,  and  the  angles  and  proportion- 
ate foreshortening  of  the  axes  used  as  the  basis  for  a  system  of 


rr=Uk5--. 
FIG.  260. — Dimetric  projection. 

pictorial  representation,  known  in  general  as  axonometric  (or 
axometric)  projection.  Isometric  projection  is  therefore  simply 
a  special  case  in  which  the  axes  are  foreshortened  equally. 

Other  positions  which  would  show  less  distortion  may  be 
chosen,  but  on  account  of  the  added  time  and  special  angles 
necessary  for  their  execution,  are  not  often  used. 

When  two  axes  are  equal,  and  the  third  unequal,  the  system 
is  sometimes  called  "dimetric"  projection.  A  simple  dimetric 
projection  in  which  the  ratios  are  1:1:1/2  is  shown  in  Fig.  260. 
In  this  position  the  tangents  of  the  angles  are  1/8  and  7/8, 
making  the  angles  approximately  7  and  41  degrees. 


134 


ENGINEERING  DRAWING 


A  simple  and  pleasing  system  known  as  clinographic  projection 
is  used  in  the  drawing  of  crystal  figures  in  mineralogy.  It  is  a 
form  of  oblique  projection  in  which  the  figure  is  imagined  as 
revolved  about  a  vertical  axis  through  an  angle  whose  tangent 
is  1/3,  then  the  eye  (at  an  infinite  distance)  elevated  through  an 
angle  whose  tangent  is  1/6.  Fig.  261  is  a  graphic  explanation. 


(1) 
cube. 

(2) 
(3) 


represents  the  top  and  front  views  of  the  three  axes  of  a 


1/3. 


is  the  top  view  revolved  through  tan- 
is  .the  side  view  of  (2) . 
(4)   is  a  front  view  projected  from  (2)  and  (3),  the  projectors 
from  (3)  being  at  tan"1  1/6. 


FIG.  261. — Analysis  of  clinographic  axes. 

When  used  in  crystallography  a  diagram  of  the  axes  is  usually 
constructed  very  accurately  on  card  board,  and  used  as  a  templet 
or^stencil,  transferring  the  center  and  terminal  points  by  pricking- 
through  to  the  sheet  on  which  the  drawing  is  to  be  made.  Fig. 
262  shows,  in  stages,  a  method  of  constructing  this  diagram, 
which  as  will  be  seen  is  simply  a  combination  in  one  view  of  2 
3,  and  4  of  Fig.  261.  Take  MON  of  convenient  length,  divide 
it  into  three  equal  parts,  at  G  and  H,  and  draw  perpendiculars  as 
shown.  Make  MS  =  1/2  MO  and  draw  SVD.  Then  CD  will  be 
one  horizontal  axis. 

Make  ML  =1/2  OG  and  draw  LO.  Project  the  point  of  inter- 
section of  LO  and  GC  back  horizontally  to  LM  at  A,  then  AOB 
will  be  the  other  horizontal  axis. 


PICTORIAL  REPRESENTATION  135 

To  obtain  length  of  vertical  axis  make  ME'  =  OG,  and  lay  off 
OE  and  OF  =  OE'. 


_^4^S$fe 


f  J^ 
^' 


FIG.  262. — Stages  of  construction  of  clinographic  axes. 

The  axial  planes,  and  some  crystals  drawn  on  these  axes,  are 
shown  in  Fig.  263. 


FIG.  263. — Crystals  in  clinographic  projection. 

These  axes  are  for  the  isometric  system  of  crystals.     Axes  for 
the  other  crystal  systems  may  be  constructed  graphically  in  the 


T 

V* 

p* 


FIG.  264. 


FIG.  265. 


same  way,  by  drawing  their  orthographic  projections,  revolving, 
and  projecting  to  the  vertical  plane  with  oblique  projectors  as 
was  done  in  Fig.  261. 


136 


ENGINEERING  DRAWING 


PROBLEMS. 

The  following  problems  are  intended  to  serve  two  purposes; 
they  are  given  first,  for  practice  in  the  various  methods  of  pictor- 


hh 


*<M 

J 


•I 


m 


FIG.  266. 


FIG.  267. 


ial  representation,  second,  for  practice  in  reading  and  translating 
orthographic  projections. 


FIG.  268. 


They  may  be  drawn  in  a  space  not  to  exceed  4x5  inches,  and 
are  arranged  in  groups  for  convenience  in  selection  and  assign- 


I 

-    ?z~- 

1 

FIG.  269. 


FIG.  270. 


ment;  but  any  of  the  figures  may,  if  desired,  be  drawn  in  one  of 
the  other  methods.  Some  of  the  figures  in  Chapter  VI  may  be 
used  for  a  still  further  variety  of  problems  in  this  connection. 


PICTORIAL  REPRESENTATION 


137 


Do  not  show  invisible  lines,  except  when  necessary  to  explain 
construction. 

Group  I. — Isometric  Drawing : 

Prob.     1.  Isometric    drawing   of   the    oil-stone,   Fig.    264. 
Full  size. 


I 


FIG.  271. 


FIG.  272. 


2.  Isometric  drawing  of  truncated  pyramid,  Fig.  265. 
Full  size. 

3.  Isometric  drawing  of  steps,  Fig.  266.  Full  size. 

4.  Isometric  drawing  of  a  1  1/2"  cube  with  circles  on 
the  three  visible  faces  (approx.  method) . 


Bottom 


FIG.  273. 


FIG.  274. 


5.  Isometric    drawing    of    brass,   Fig.    267.     Scale 
6"=!'. 

6.  Isometric  drawing  of  bracket,  Fig.  268.    Full  size. 
Prob.     7.  Isometric  drawing  of  brick,  Fig.  269.     Full  size. 

8.  Isometric  drawing  of  brick,  Fig.  270.     Full  size. 


138 


ENGINEERING  DRAWING 


9.  Isometric  drawing  of  core  box,  Fig.  271.  Full  size. 

10.  Isometric  drawing  of  block,  Fig.  272.  Full  size. 

11.  Isometric  drawing  of  knee  brace,  Fig.  273.  Scale 
1/2"=!'. 


Boffom  ^/ens 


FIG.  275. 

12.  Isometric  drawing  of  mitered  corner  (face  return), 
Fig.  274;  axes  reversed  to  show  under  side.  Scale 
6"=!'. 

13.  Isometric  drawing  of  stone   (springing  stone  of 
plate  band,  or  flat  arch)  Fig.  275,  axes  reversed. 
Full  size. 


FIG.  276. 


FIG.  277. 


Group  II. — Isometric  Sections : 

Prob.  14.  Isometric  section  of  cap,  Fig.  276.     Scale  3"=!'. 
15.   Isometric    section    of    pulley,    Fig.    277.     Scale 
6"=!'. 


PICTORIAL  REPRESENTATION 


139 


16.  Isometric  half-section  of  cone,  Fig.  278.     Scale 
6"=!'. 

17.  Isometric  half-section  of  gland,  Fig.  279.     Scale 
6"=!'. 


FIG.  278. 

Group  III. — Oblique  Drawing: 

Prob.   18.  Oblique  drawing  of  block,  Fig.  280,  30  degrees  to 
the  left.     Full  size. 

19.  Oblique  drawing  of  block,  Fig.  281,  30  degrees  to 
the  right,  full  size. 

20.  Oblique  drawing  of  grindstone,  Fig.  282,  45  de- 
grees to  the  right.     Scale  1"=!'. 


FIG.  280. 

21.  Oblique  drawing  of  1  1/2"  cube,  30  degrees  to  the 
right,    with    circles    on    the    three    visible    faces 
(approximate) . 

22.  Oblique  drawing  of  1  1/2"  cube,  45  degrees  to  the 
left,  with  circles  on  three  visible  faces  (approxi- 
mate) . 

23.  Oblique  drawing  of  column  section,  Fig.  283,  30 
degrees  to  the  left.     Scale  1  1/2"=  I'. 

24.  Oblique    drawing    of    monument,    Fig.    284,    30 
degrees  to  the  right.     Scale  1/2"=!'.      . 


140 


ENGINEERING  DRAWING 


25.  Oblique  drawing  of  gland,  Fig.  285,  45  degrees 
to  the  right.     Full  size. 

26.  Oblique    drawing    of    angle  brace,    Fig.   286,  30 
degrees  to  the  left.     Scale  6"=  I'. 


FIG.  282. 


FIG.  283. 


FIG.  285. 


FIG.  284. 


Ttr  Hfrai 


tl^g 


FIG.  286. 


27.  Oblique   drawing   of   slotted   link,   Fig.    287,  30 
degrees  to  the  left.     Scale  1  1/2"=  1'. 

28.  Oblique    drawing    of    bell-crank,    Fig.    288,    45 
degrees  to  the  left.     Scale  6"=!'. 


PICTORIAL  REPRESENTATION 


141 


29.  Oblique  drawing  of  link,  Fig.  289,  30  degrees  to 
the  right.     Full  size. 

30.  Oblique  drawing  of  cap,  Fig.  290,  45  degrees  to 
the  left.     Scale  6"=!'. 


FIG.  287. 


FIG.  291. 


FIG.  290. 


FIG.  292. 


31.  Oblique  drawing  of  cam,  Fig.  291,  30  degrees  to 
the  right.     Scale  3"=  V . 

32.  Oblique  drawing  of  bearing.     Fig.  292,  30  degrees 
to  the  right.     Scale  6"=!'. 


142 


ENGINEERING  DRAWING 


33.  Oblique    drawing    of    moulded    brick    and    face 
return,  Fig.  293,  45  degrees  to  the  right,  axes 
reversed  to  show  under  side.     Scale  3"  =  !'. 

34.  Oblique  drawing  of  culvert   arch,   Fig.   294,   30 
degrees  to  the  left,  draw  by  offsets  from  right 
section.     Full  size. 


•  s- 


I-*"' 


T 

*o 

L 


FIG.  293. 


i 


i 


1 


==$ 


FIG.  295. 


FIG.  294. 


ftf" 


//* 


— S-4-'- 
-a-7£- 


FIG.  296. 


FIG.  297. 


FIG.  298. 


Group  IV.— Cabinet  and  Dimetric  Projection. 

Prob.   35.   Cabinet    projection   of   frame,  Fig.   295.     Scale 
3/4"=!'. 


PICTORIAL  REPRESENTATION 


143 


144 


ENGINEERING  DRAWING 


36.  Cabinet    projection    of    desk,    Fig.    296.     Scale 
1"  =  !'. 

37.  Dimetric  Projection  of  table,  Fig.    297.     Scale 
3/4"=!'. 

38.  Dimetric  projection  of  Roman  chair,  Fig.   298. 
Scale    1"=!'. 


J  L 


FIG.  300. — Reading  exercises. 

Group  V. — Reading  Exercises. 

Assuming  that  the  student  is  now  familiar  with  the  methods 
of  pictorial  representation,  the  objects  in  Fig.  299  and  300  are 
given  to  test  further  the  ability  to  read  orthographic  projec- 
tions, by  sketching  the  figures  shown,  in  any  one  of  the  pictorial 
systems. 

Some  may  be  read  at  a  glance,  others  will  require  careful  com- 
parison of  the  different  views  before  the  mental  image  of  the 
object  is  clearly  defined.' 


CHAPTER  IX. 
WORKING  DRAWINGS. 

A  working  drawing  is  a  drawing  that  gives  all  the  information 
necessary  for  the  complete  construction  of  the  object  represented. 

It  will  thus  include:  (1)  The  full  graphical  representation  of 
the  shape  of  every  part  of  the  object.  (2)  The  figured  dimen- 
sions of  all  parts.  (3)  Explanatory  notes  giving  specifications 
in  regard  to  material,  finish,  etc.  (4)  A  descriptive  title. 

Although  isometric,  oblique  and  cabinet  drawing  are  used  to 
some  extent  in  special  cases,  the  basis  of  practically  all  working 
drawing  is  orthographic  projection.  To  represent  an  object 
completely,  at  least  two  views  would  be  necessary,  often  more. 
The  only  general  rule  would  be,  make  as  many  views  as  are 
necessary  to  describe  the  object,  and  no  more. 

Instances  may  occur  in  which  the  third  dimension  is  so  well 
understood  as  to  make  one  view  sufficient,  as  for  example  in  the 
drawing  of  a  shaft  or  bolt.  In  other  cases  perhaps  a  half  dozen 
views  might  be  required  to  show  the  piece  completely.  Some 
thought  will  be  involved  as  to  what  views  will  show  the  object 
to  the  best  advantage;  whether  an  auxiliary  view  will  save  one 
or  more  other  views,  or  whether  a  section  will  better  explain  the 
construction  than  an  exterior  view.  One  statement  may  be 
.made  with  the  force  of  a  rule — If  anything  in  clearness  may  be 
gained  by  the  violation  of  any  one  of  the  strict  principles  of 
projection,  violate  it. 

This  statement  is  of  sufficient  importance  to  warrant  several 
examples,  although  there  is  no  guide  but  the  draftsman's  judg- 
ment as  to  when  added  clearness  might  result  by  disregarding  a 
theoretical  principle. 

If  a  six-arm  wheel,  Fig.  301,  be  shown  in  section  as  if  cut  by  a 

plane  A- A,  the  true  projection  would  be  as  A;  if  cut  by  a  plane 

B-B  the  true  projection  would  be  as  B.     Neither  of  these  would 

be  good  practical  working  drawings,  the  first  does  not  show  the 

10  145 


146 


ENGINEERING  DRAWING 


true  size  of  the  arm,  the  second  is  misleading.     The  sectional 
view  whether  taken  on  A-A  or  B-B  would  be  better  if  made  as  C. 


(NOT) 


FIG.  302. — Section  through  a  rib. 


Similarly,  if  a  section  taken  through  a  rib,  as  the  section  S-S 
of  the  piston,  Fig.  302,  is  cross-hatched  as  in  A  the  effect  is  mis- 
leading. Its  character  may  be  indicated  much  better  by 


WORKING  DRAWINGS 


147 


omitting  the  lining  on  the  rib,  as  if  the  section  were  just  in  front 
of  it,  as  at  B,  or  by  running  every  other  line  across  the  rib 
section,  as  at  C. 

Often  a  true  section  would  give  an  unsymmetrical  appearance 
to  the  drawing  of  a  symmetrical  piece.  In  such  cases  principle 
should  be  violated  to  preserve  the  effect  of  symmetry.  Fig.  303 
is  an  illustration. 


(NOT)  B 


FIG.  303.  —  A  symmetrical  section. 


Classes  of  Working  Drawings. 

Working  drawings  may  be  divided  into  two  general  classes, 
assembly  drawings  and  detail  drawings. 

An  assembly  drawing  or  general  drawing  is,  as  its  name  implies, 
a  drawing  of  the  machine  or  structure  showing  the  relative 
positions  of  the  different  parts. 

A  detail  drawing  is  the  drawing  of  a  separate  piece  or  group  of 
pieces,  giving  the  complete  description  for  the  making  of  each 
piece.  In  a  very  simple  machine  the  assembly  drawing  may  be 
made  to  serve  as  a  detail  drawing  by  showing  fully  the  form  and 
dimensions  of  each  part  composing  it. 

Under  the  general  term  assembly  drawing  would  be  included 
preliminary  design  drawings  and  layouts,  piping  plans,  and  final 
complete  drawings  used  for  assembling  or  erecting  the  machine 
or  structure. 

The  design  drawing  is  the  preliminary  layout,  full  size  if 
possible,  on  which  the  scheming,  inventing,  and  designing  is 
worked  out  accurately  after  freehand  sketches  have  determined 
the  general  ideas.  From  it  the  detail  drawings  of  each  piece  are 
made.  The  design  drawing  may  be  finished  and  traced  to  form 
the  assembly  drawing,  or  the  assembly  drawing  may  be  drawn 
from  it,  perhaps  to  smaller  scale  to  fit  a  standard  sheet. 


148  ENGINEERING  DRAWING 

The  assembly  drawing  would  give  the  over-all  dimensions,  the 
distances  from  center  to  center  or  from  part  to  part  of  the 
different  pieces,  indicating  their  location  and  relation  so  that  the 
machine  could  be  erected  by  reference  to  it. 

The  grouping  of  the  details  is  entirely  dependent  upon  the 
requirements  of  the  shop  system.  In  a  very  simple  machine 
and  if  only  one  or  two  are  to  be  built,  all  the  details  may  perhaps 
be  grouped  on  a  single  sheet.  If  many  are  to  be  built  from  the 
same  design,  each  piece  may  have  a  separate  sheet.  In  general, 
it  is  a  good  plan  to  group  the  parts  of  the  same  material  or 
character.  Thus  forgings  may  be  grouped  on  one  sheet,  bolts 
and  screws  on  another. 

A  complete  set  of  working  drawings  therefore  consists  of 
assembly  sheets,  and  detail  sheets  for  each  of  the  classes  of  work- 
men, as  the  patternmaker,  blacksmith,  machinist,  etc.  These 
special  drawings  need  not  include  dimensions  not  needed  by 
those  trades.  The  set  may  include  also  drawings  for  the 
purchaser. 

There  is  a  "style"  in  drawing,  just  as  there  is  in  literature, 
which  in  one  way  indicates  itself  by  the  ease  of  reading.  Some 
drawings  "  stand  out,"  while  others  which  may  contain  all  the 
information  are  difficult  to  decipher.  Although  dealing  with 
"mechanical  thought,"  there  is  a  place  for  some  artistic  sense  in 
mechanical  drawing.  The  number,  selection,  and  disposition  of 
views,  the  omission  of  anything  unnecessary,  ambiguous,  or 
misleading,  the  size  and  placing  of  dimensions  and  lettering,  and 
the  contrast  of  lines  are  all  elements  concerned  in  the  style. 
Order  of  Penciling. 

In  penciling  a  working  drawing  the  order  should  be  as  follows : 
first,  lay  off  the  sheet  to  standard  size,  with  border  (1/2  inch), 
and  block  out  space  for  the  title;  second,  plan  the  arrangement 
by  making  a  little  preliminary  freehand  sketch,  guessing  roughly 
at  the  space  each  figure  will  occupy,  and  placing  the  views  to  the 
best  advantage  for  preserving  if  possible  a  balance  in  the  appear- 
ance of  the  sheet;  third,  draw  the  center  lines  for  each  view,  and 
on  these  lay  off  the  principal  dimensions.  In  Chapter  VI  the 
general  principle  was  given  that  the  view  showing  the  character- 
istic shape  should  be  made  first.  The  different  projections  should 
however  be  carried  on  together  and  no  attempt  made  to  finish 
one  view  before  drawing  another.  Fourth,  finish  the  projections, 


WORKING  DRAWINGS 


149 


putting  in  minor  details  last;  fifth,  draw  the  necessary  dimension 
lines  and  add  the  dimensions;  sixth,  lay  off  the  title;  seventh, 
check  the  drawing  carefully. 

Fig.  304  illustrates  the  stages  of  penciling  a  drawing.     Over- 
lapping and  overextending  pencil  marks  should  not  be  erased 


FIG.  304.— Stages  of  penciling. 

until  after  the  drawing  has  been  inked.  These  extensions  are 
often  convenient  in  preventing  the  overrunning  of  ink  lines.  All 
unnecessary  erasing  should  be  avoided  as  it  abrades  the  surface, 
of  the  paper  so  that  dirt  catches  more  readily. 


FIG.  305.— Stages  of  inking. 

Order  of  Inking. 

First,  ink  all  circles,  then  circle  arcs;  second,  ink  the  straight 
lines  in  the  order, — horizontal,  vertical,  inclined;  third,  ink  center 
lines;  extension  and  dimension  lines;  fourth,  ink  the  dimensions; 
fifth,  section  line  all  cut  surfaces;  sixth,  ink  notes,  title,  and 
border  line;  seventh,  check  the  tracing.  Figure  305  shows  the 
stages  of  inking. 


150  ENGINEERING  DRAWING 

DIMENSIONING. 

After  the  correct  representation  of  the  object  by  its  projec- 
tions, the  entire  value  of  the  drawing  as  a  working  drawing  lies 
in  the  dimensioning.  Here  our  study  of  drawing  as  a  language 
must  be  supplemented  by  a  knowledge. of  the  shop  methods 
which  will  enter  into  the  construction.  The  draftsman  to  be 
successful  must  have  an  intimate  knowledge  of  pattern  making, 
forging,  sheet  metal  working  and  machine  shop  practice. 

The  dimensions  put  on  a  drawing  are  not  those  which  were 
used  in  making  it,  but  those  necessary  and  most  convenient  for 
the  workman  who  is  to  make  the  piece.  The  draftsman  must 
thus  put  himself  in  the  place  of  the  pattern  maker,  blacksmith  or 
machinist,  and  mentally  construct  the  object  represented,  to 
see  if  it  can  be  cast  or  forged  or  machined  practically  and  eco- 
nomically, and  what  dimensions  would  give  the  required  infor- 
mation in  the  best  way.  In  brief,  the  drawing  must  be  made 
with  careful  thought  of  its  purpose. 
General  Rules  for  Dimensioning. 

In  the  alphabet  of  lines  in  Fig.  62  the  dimension  line  was  shown 
as  a  fine  full  line,  with  long  arrow  heads  whose  extremities 
indicate  exactly  the  points  to  which  the  dimension  is  taken,  and 
having  a  space  left  for  the  figure. 

Some  practice  uses  a  long  dash  line,  and  some  a  red  line  for 
dimension  lines.  It  is  common  practice  among  structural 
draftsmen  to  place  the  dimension  above  the  continuous  line  as 
in  Fig.  346,  but  it  is  not  recommended  for  machine  or  architec- 
tural work. 

Dimensions  of  course  always  indicate  the  finished  size  of  the 
piece,  without  any  reference  to  the  scale  of  the  drawing. 

Dimensions  should  read  from  the  bottom  and  right  side  of  the 
sheet,  no  matter  what  part  of  the  sheet  they  are  on. 

Dimensions  up  to  24"  should  always  be  given  in  inches.  An 
exception  is  again  noted  in  structural  practice.  Over  24" 
practice  varies,  but  the  majority  use  feet  and  inches.  The  sizes 
of  wheels,  gears,  pulleys  and  cylinder  bores,  the  stroke  of  pistons, 
and  the  length  of  wheel  bases  are  always  given  in  inches;  and 
sheet  metal  work  is  usually  dimensioned  in  inches. 

Feet  and  inches  are  indicated  thus  5'-6"  or  5  ft.-6".  When 
there  are  no  inches,  it  should  be  indicated  as  5'-0",  5'-(H". 


WORKING  DRAWINGS 


151 


Fractions  must  be  made  with  a  horizontal  line  as  2J", 

The  diameter  of  a  circle  should  be  given,  not  the  radius. 

In  general  give  dimensions  from  center  lines,  never  from  the 
edge  of  a  rough  casting. 

Have  figures  large  enough  to  be  easily  legible.  In  an  effort 
for  neatness  the  beginner  often  gets  them  too  small. 

Radii  of  arcs  should  be  marked  It  or  Had. 

Dimensions  should  generally  be  placed  between  views. 


~j 

<Vj 

t, 

J^ 

i 

u 

f- 

t 

'*   p 

vv 

3" 

// 

H             •& 

FIG.  306. — Example  of  dimensioning. 

In  general  do  not  repeat  dimensions  on  adjacent  views. 

Preferably  keep  dimensions  outside  the  figure  unless  added 
clearness,  simplicity,  and  ease  of  reading  the  drawing  will  result 
from  placing  them  in  the  figure.  See  Fig.  306.  Keep  them  off 
sectioned  surfaces  if  possible. 

Extension  lines  should  not  touch  the  outline. 

Always  give  an  over-all  dimension.  Never  require  the  work- 
man to  add  or  subtract  figures. 

Never  use  any  center  line  as  a  dimension  line. 

Never  put  a  dimension  on  a  line  of  the  drawing. 

A  dimension  not  agreeing  with  the  scaled  distance,  or  which 
has  been  changed  after  the  drawing  has  been  made  should  be 
heavily  underscored  as  in  Fig.  307  (2) ,  or  marked  as  in  (3) . 


152 


ENGINEERING  DRAWING 


Dimensions  must  never  be  crowded.  If  the  space  is  small, 
methods  as  illustrated  in  Fig.  307  (4)  (5)  (6)  (9),  etc.,  may  be  used. 

The  direction  in  which  a  section  is  taken  should  be  indicated 
by  arrows  on  the  line  representing  the  cutting  plane,  as  in  (29). 

If  it  is  possible  to  locate  a  point  by  dimensions  from  two  center 
lines,  do  not  give  an  angular  dimension. 


NOT  THUS 


© 


"/H   h*H  -UTI-  Hh/ 

©  (D  ©  © 


© 


@ 


FHl-fHl   J^ 

©  © 

FIG.  307. — Dimensions. 


The  Finish  Mark. 

Several  methods  are  used  for  indicating  that  certain  parts  are 
to  be  machined,  and  that  allowance  must  therefore  be  made  on 
the  casting  or  forging  for  finish.  The  symbol  in  common  use  is 
a  small  "f"  placed  on  the  surface,  on  the  view  which  shows  the 
surface  as  a  line,  Fig.  307  (26).  If  the  piece  is  to  be  finished  all 
over,  the  note  "f.  all  over"  is  placed  under  it,  and  the  marks 
on  the  drawing  omitted. 

Another  finish  mark,  proposed  by  Professor  Follows  for 
adoption  as  a  standard,  is  shown  at  (27).  It  has  a  distinct 
individuality,  and,  by  pointing  to  the  line  instead  of  crossing  it, 
does  not  mar  the  appearance  of  the  drawing  as  the  "f "  does. 
The  symbol  as  used  in  (28)  indicates  that  the  entire  surface 
between  the  extension  lines  is  to  be  finished. 

Some  elaborate  symbols  for  different  kinds  of  finish  have  been 
devised,  but  it  is  much  better  to  specify  these  in  words. 

Notes  and  Specifications. 

Some  necessary  information  cannot  be  drawn,  and  hence 
must  be  added  in  the  form  of  notes.  This  would  include  the 


WORKING  DRAWINGS  153 

number  required  of  each  piece,  the  kind  of  material,  kind  of 
finish,  kind  of  fit  (as  force  fit,  drive  fit,  etc.),  and  any  other 
specifications  as  to  its  construction  or  use. 

Do  not  be  afraid  of  putting  notes  on  drawings.  Supplement 
the  graphic  language  by  the  English  language  whenever  added 
information  can  be  conveyed,  but  be  careful  to  word  it  so  clearly 
that  the  meaning  cannot  possibly  be  misunderstood. 

If  a  note  as  to  the  shape  of  a  piece  will  save  making  a  view, 
use  it. 

If  two  pieces  are  alike,  but  one  " right-hand"  and  the 'other 
"left-hand,"  one  only  is  drawn  and  a  note  added  1-R.  H.,  1-L.  H. 

Standard  bolts  and  screws  are  never  detailed,  but  are  specified 
in  the  bill  of  material. 

The  bill  of  material  is  a  tabulated  statement  placed  on  a  draw- 
ing, or  in  some  cases,  for  convenience,  on  a  separate  sheet,  which 
gives  the  mark,  name,  number  wanted,  size,  material,  pattern 
number,  and  sometimes  the  weight,  of  each  piece.  A  column 
giving  the  over-all  dimensions  of  the  piece  when  crated  or  boxed 
for  shipping  is  sometimes  added,  particularly  in  manufactures 
for  foreign  shipment.  A  final  column  is  usually  left  for 
"  remarks." 

Fig.  308  is  a  detail  drawing  illustrating  the  use  of  the  bill  of 
material. 

Title.* 

The  title  to  a  working  drawing  is  usually  boxed  in  the  lower 
right  hand  corner,  the  size  of  the  space  varying  of  course  with 
the  size  of  the  drawing.  For  12"xl8"  sheets  the  space  reserved 
may  be  about  three  inches  long.  For  18"x24"  sheets  four  or 
four  and  a  half,  and  for  24"x36"  sheets  five  or  five  and  a  half 
inches. 

A  form  of  title  which  is  growing  in  favor  is  the  record  strip, 
a  narrow  strip  marked  off  entirely  across  the  lower  part  of  the 
sheet,  containing  the  information  required  in  the  title,  and 
ample  space  for  the  record  of  orders,  changes,  etc.  Fig.  309 
illustrates  this  form. 

It  is  sometimes  desired  to  keep  records  of  orders  and  other 
private  information  on  the  tracing,  but  not  have  them  appear 

*For  a  full  discussion  of  titles  for  different  classes  of  drawings  see  "The 
Essentials  of  Lettering/'  from  which  this  paragraph  is  condensed. 


154 


ENGINEERING  DRAWING 


WORKING  DRAWINGS 


155 


on  the  print.  In  such  case  both  the  corner  title  and  record 
strip  are  used,  and  the  record  strip  trimmed  off  the  print  before 
sending  it  out. 

Contents  of  Title. 

In  general  the  title  of  a  machine  or  structural  drawing  should 
contain: 

(1)  Name  of  machine  or  structure. 

(2)  General  name  of  parts  (or  simply  " details"). 


B895/ 

THE  THOMPSON  A  UTOMOB/LE  CO.,  DETffO/T.  M/CH.     \  Sca/e  6*/  ' 

<Z»i&t<*ur^ 

_/J  S.  a    J<42S 
0  Chonyeet  from  /O* 
©  Change*  from  /£" 

2} 

3J 

CAR  A-6-6O-// 

D£T^li- 

C.YLJMDE.F3S 

5gX5~ 

T"^ji^^L. 

CHg£S&^ 

FIG.  309.— A  record  strip. 

(3)  Name  of  purchaser,  if  special  machine.   - 

(4)  Manufacturer;  company  or  firm  name  and  address, 

(5)  Date;  usually  date  of  completion  of  tracing. 

(6)  Scale   or  scales;   desirable   on  general  drawings,   often 
omitted  from  fully  dimensioned  detail  drawings. 

(7)  Drafting  room  record;  names,  initials  or  marks  of  the 
draftsman,  tracer,  checker,  approval  of  chief  draftsman, 
engineer  or  superintendent. 


The  Jeffrey  Mfg.  Co. 

COLUMBUS,    OHIO.   U.  S.  A. 

Engineering  Department. 

CONVEYING  AND  ELEVATING  MACHINERY. 

SCALE 

DIRECTED 

APPROVED  ..    . 

TRACED      "    

CHECKED  "    
CORRECT  "    _  

FIG.  310. — A  printed  title  form. 

(8)  Numbers;  of  the  drawing,  of  the  order.  The  filing 
number  is  often  repeated  in  the  upper  left  hand  corner 
upside  down,  for  convenience  in  case  the  drawing  should 
be  reversed  in  the  drawer. 


15G  ENGINEERING  DRAWING 

The  title  should  be  lettered  freehand  in  single  stroke  capitals, 
either  upright  or  inclined,  but  never  both  styles  in  the  same  title. 

Any  revision  or  change  in  the  drawing  should  be  noted,  with 
date,  in  the  title  or  record  strip. 

Every  drafting  room  has  its  own  standard  form  for  titles. 
In  large  offices  this  is  often  printed  in  type  on  the  tracing  cloth. 
Figs.  310  and  311  are  characteristic,  examples. 

Sometimes  a  title  is  put  on  with  a  rubber  stamp,  and  inked 
over  while  wet. 


GENERAL  NOTES. 


WORKMANSHIP- 
MATERIAL 


CONTRACT. 

SHEET  No, 


ASSEMBLING  PAINT- 
SHOP PAINT 

FIELD  PAINT 


BUILT  BY 

KING  BRIDGE  COMPANY 


FIELD  CONNECTION* CLEVELAND,  OHIO 

F.O.  B 

SHIP __^    DRAWINGS  FINISHED 


o 


FIG.  311. — A  printed  title  form. 

In  commercial  drafting,  accuracy  and  speed  are  the  two  require- 
ments. The  drafting  room  is  an  expensive  department,  and 
time  is  an  important  element.  The  draftsmen  must  therefore 
have  a  ready  knowledge  not  only  of  the  principles  of  drawing, 
but  of  the  conventional  methods  and  abbreviations,  and  any 
device  or  system  that  will  save  time  without  sacrificing  effective- 
ness, is  desirable. 


FASTENINGS. 

In  every  working  drawing  will  occur  the  necessity  of  repre- 
senting the  methods  of  fastening  parts  together,  either  with 
permanent  fastenings  (rivets)  or  with  removable  ones  (bolts, 
screws  and  keys),  and  the  draftsman  must  be  thoroughly  familiar 
with  the  conventional  methods  of  their  representation. 


WORKING  DRAWINGS 


157 


The  Helix. 

A  helix  is  the  line  of  double  curvature  generated  by  a  point 
moving  uniformly  along  a  straight  line  while  the  line  revolves 
uniformly  about  another  line,  as  an  axis. 

The  distance  advanced  parallel  to  the  axis  in  one  revolution  is 
called  the  pitch.  If  the  moving  line  is  parallel  to  the  axis  it  will 
generate  a  cylinder,  and  the  word  "helix"  alone  always  means 
a  cylindrical  helix.  If  the  moving  line  intersects  the  axis  (at  an 
angle  less  than  90  degrees)  it  will  generate  a  cone  and  the  curve 
made  by  the  moving  point  will  be  a  conical  helix.  When  the 
angle  becomes  90  degrees  the  helix  degenerates  into  a  spiral. 


f  2  3  4  5  6  7  S  9  /O///2/ 


FIG.  312. — Construction  of  the  helix. 

To  Draw  a  Helix. — Divide  the  circle  of  the  base  of  the  cylinder 
into  a  number  of  equal  parts,  and  the  pitch  into  the  same  number. 
As  the  point  revolves  through  one  division  it  will  advance  one 
division  of  the  pitch,  when  half  way  around  the  cylinder  it  will  have 
advanced  one-half  the  pitch.  Thus  the  curve  may  be  found  by 
projecting  the  elements  represented  by  the  divisions  of  the  Circle, 
to  intersect  lines  drawn  through  the  corresponding  divisions  of 
the  pitch,  as  in  Fig.  312. 

The  conical  helix  is  drawn  similarly,  the  pitch  being  measured 
on  the  axis. 

Screw  Threads. 

The  helix  is  the  curve  of  the  screw  thread,  but  is  not  often 
drawn,  and  only  with  screws  of  large  diameter.  Fig.  313 
illustrates  its  application  on  a  square  thread  screw  and  section  of 


158 


ENGINEERING  DRAWING 


nut.  Two  helices  of  the  same  pitch  but  different  diameters  are 
required,  one  for  the  tip  and  one  for  the  root  of  the  thread.  If 
many  threads  are  to  be  drawn,  a  templet  may  be  made,  by  laying 
off  the  projection  of  the  helix  on  a  piece  of  cardboard,  and  cutting 
out  with  a  sharp  knife. 

Fig.  314  shows  the  method  of  drawing  a  helical  spring  with 
round  section,  by  constructing  the  helix  of  the  center  line  of  the 


FIG.  313. — Construction  of  square  thread. 

section,  drawing  on  it  a  number  of  circles  of  the  diameter  of  the 
stock,  and"  drawing  an  envelope  curve  tangent  to  the  circles. 

Forms  of  Threads. 

Screws  are  used  for  fastenings,  for  adjustment,  and  for  trans- 
mitting power  or  motion.  For  these  different  purposes  several 
different  forms  of  thread  are  in  use.  The  United  States  Standard 


FIG.  314. 

(sometimes  called  the  Franklin  Institute,  and  Sellers  standard), 
Fig.  315,  A,  is  the  commonest,  and  in  this  country  is  the  form 
intended  when  not  otherwise  specified.  It  is  a  V  thread  at 
60  degrees  with  the  tip  flattened  one-eighth  of  its  height,  which 
lessens  the  liability  of  its  being  injured,  and  the  root  filled  the 
same  amount,  thus  increasing  the  strength  of  the  bolt.  In 
drawing,  these  flats  need  not  be  represented. 


WORKING  DRAWINGS 


159 


The  sharp  V  at  60  degrees  is  still  used,  although  it  has  little^to 
recommend  it.  The  square  thread  and  the  Acme  or  Powell 
thread  are  used  mainly  to  transmit  motion.  Other  forms  shown 
are  the  buttress,  knuckle,  and  Whitworth,  the  English  standard. 


fA)    U.  S.  STANDARD 
-P 


SHARP    V 


SQUARE 


KNUCKLE  WH/TWOGTH 

FIG.  315. — Forms  of  screw  threads. 

Threads  are  always  understood  to  be  single  and  right  hand 
unless  otherwise  specified. 

A  right  hand  thread  advances  away  from  the  body  when  turned 
clockwise.  A  left  hand  thread  is  always  marked  plainly  "L  H," 
and  is  quickly  recognized  also  by  the  direction  of  slant. 


FIG.  316. — Conventional  threads. 


A  single  thread  has  one  thread,  of  whatever  section,  winding 
around  the  cylinder.  When  it  is  desired  to  give  a  more  rapid 
advance  without  using  a  coarser  thread,  two  or  more  threads  are 
wound  together,  side  by  side,  giving  double  and  triple  threads,  as 
illustrated  in  Fig.  316,  C  and  D. 


160 


ENGINEERING  DRAWING 


Conventional  Representation  of  Threads. 

For  ordinary  practice  the  labor  of  drawing  the  exact  curves  of 
threads  is  altogether  unnecessary,  and  the  helix  is  conventional- 
ized into  a  straight  line.  The  square  thread  screw  would  thus 


WfiMffi 


.-V£- 


M       4/T/l/l/j/M/Vl      -^W^^^      fjTWK'^i^ 

""  UU-    4^-n-   iuU-Sm    4|%Wi% 

ill          /U/llllvl      4/1^474^AiA4/      ^H^lMWJ> 


Hiwk- 

FIG.  317. — Stages  in  drawing  V  threads. 

be  drawn  as  in  Fig.  316  (A)  or  (B),  which  while  not  so  realistic 
or  pleasing  as  Fig.  313,  requires  very  much  less  time. 

The  V  thread  would  be  drawn,  both  in  pencil  and  ink,  in  the 
stages  shown  in  Fig.  317. 


For  screws  less  than  perhaps  one  inch  in  diameter,  the  thread 
shapes  are  omitted  and  one  of  the  conventional  forms  of  Fig.  318 
used..  A  is  a  very  common  convention.  The  lines  are  drawn 
with  a  slight  slant  (one-half  the  pitch),  and  spaced  by  eye.  The 


FIG.  319.— Tapped  hoi 


spacing  need  not  be  to  the  correct  pitch,  but  to  look  well  should 
somewhat  approximate  it. 

The  root  lines  are  usually  made  heavier,  for  effect.  The 
beginner's  usual  mistake  of  exaggerating  the  slant  must  be  care- 
fully guarded  against.  It  is  a  question  as  to  whether  there  is 


WORKING  DRAWINGS 


161 


any  necessity  of  slanting  the  lines  at  all,  and  in  much  good 
practice  they  are  drawn  straight  across. 

B  is  a  simpler  convention,  in  that  it  requires  no  pencil  lines 
for  limiting  the  root  lines,  as  there  is  always  a  center  line  already 
drawn.  In  this  the  root  lines  are  always  placed  on  the  shade 
side. 

C  is  a  convention  that  does  not  look  like  a  thread,  but  that  can 
be  made  rapidly,  and  is  understood  by  all  workmen. 

Fig.  319  shows  the  conventional  representation  of'  tapped 
holes  in  plan,  section  and  elevation.  In  showing  a  tapped  hole 


FIG.  320. 


in  section  the  slant  of  the  thread  lines  would  evidently  be  reversed 
as  the  part  represented  fits  the  invisible  side  of  the  screw.  In 
tapped  holes  not  extending  through  the  piece,  the  "drill  point," 
or  shape  of  the  bottom  of  the  hole  should  always  be  shown. 

When  two  pieces  fitted  together  are  shown  in  section  the 
threads  must  be  drawn,  as  in  Fig.  320.  The  same  is  true  for  a 
male  thread  in  section. 

It  is  not  necessary  to  draw  the  threads  on  the  whole  length  of 
a  long  threaded  shaft.     They  may  be  started  at  each  end,  and 
" ditto"  lines  used  in  the  space  between. 
11 


162 


ENGINEERING  DRAWING 


Dimensioning  Threads. 

If  a  thread  is  U.  S.  Standard  the  only  dimensions  given  are 
the  outside  diameter  and  the  length.  When  these  dimen- 
sions are  given  the  thread  is  always  assumed  to  be  U.  S. 
Standard  right  hand,  and  the  machinist  knows  the  pitch,  drill 
sizes,  etc.  The  word  "pitch"  has  been  defined  as  the  distance 
between  threads.  A  commonly  accepted  meaning  among 
machinists  is  the  number  of  threads  per  inch,  thus  "8  pitch" 
would  mean  eight  threads  per  inch.  There  is  very  little  danger 
of  misunderstanding  in  these  two  meanings,  but  it  may  be  safer, 

particularly  in  screws  of  large  diameter,  to  say  " threads 

per  in." 


FIG.  321.— U.  S.  Standard  bolts  (unfinished). 

With  double  and  triple  threads  "pitch"  is  generally  accepted 
to  mean  the  distance  between  adjacent  threads,  and  the  distance 
advanced  in  one  revolution  is  called  the  "lead." 

A  distinction  in  designation  should  be  made  between  tapped 
holes  and  threaded  holes. 

Bolts  and  Nuts. 

There  are  adopted  sizes  for  standard  hexagonal  and  square 
bolt  heads  and  nuts,  hence  on  a  standard  bolt  no  dimensions  are 
placed  except  the  diameter,  length  (under  the  head  to  tip  of 
point),  and  length  of  threaded  part.  As  there  is  so  frequent 
necessity  for  the  representation  of  bolts  and  screws  the  drafts- 
man must  be  able  to  draw  them  without  reference  to  tables  or 
measurement. 


WORKING  DRAWINGS 


163 


Fig.  321  shows  the  U.  S.  Standard  hex.  head,  and  the  stand- 
ard square  head  bolt  and  nut.  In  drawing  a  hex.  head  three 
faces  are  shown,  and  in  a  square  head,  one  face. 


DIMENSIONS  OF  U.  S.  STANDARD  BOLTS  AND  NUTS. 


Diam. 
of 
bolt 

Thrd's 
per 
inch 

Distance 
across 

flats 

Distance 
across  corners 

Thickness 

Area  at 
root  of 
thread 

Hexagon 

Square 

Nut 

Head 

F 

20 

I" 

tr 

ir 

r 

F 

.026 

iV 

18 

w 

H* 

w 

TV 

if 

.045 

t" 

16 

w 

ir 

w 

r 

H" 

.068 

Ty 

14 

tr 

tr 

w 

7  '/ 
TV 

ir 

.093 

F 

13 

r 

W 

ir 

F 

TV" 

.126 

iV 

12 

tr 

ir 

ir 

T9/ 

IF 

.162 

r 

11 

W 

nr 

if 

r 

IF. 

.202 

f 

10 

IF 

iff 

itr 

r 

F 

.302 

F 

9 

W 

'  itr 

2^/ 

F 

IF 

.420 

i" 

8 

ir 

if" 

2H* 

ir/ 

if 

.550 

IF 

7 

iir 

S// 

2T9/ 

IF 

IF 

.693 

IF 

7 

2* 

2T5/ 

2ff" 

H" 

1* 

.889 

ir 

6 

2A" 

2ir 

333/ 

if 

1A" 

1.054 

IF 

6 

2f 

2f 

3ff 

IF 

1T3F 

1.293 

ir 

5 

2f 

3T3/ 

sir 

if 

if 

1.744 

2" 

4i 

sr 

3ir 

4§r 

2" 

1T9F 

2.302 

164 


ENGINEERING  DRAWING 


A  quick  method  of  penciling  a  standard  hex.  head  or  nut  is 
shown  in  stages  in  Fig.  322.     Mark  a  point  on  the  center  line  at 


LLTJ 

I ~ezz&    * 


FIG.  322. — A  method  of  drawing  a  hexagonal  head. 

a  distance  1  1/2D  +  1/8".  Sixty-degree  lines  drawn  from  this 
point  to  the  base  will  give  points  for  the  outside  corners.  The 
remainder  of  the  construction  is  evident  from  the  figure. 


CTTJ 


LCD 


r 


m 


FIG.  323. — Locknuts. 

It  is  evident  from  geometry  that  the  projected  width  of  the 
inclined  face  is  one  half  that  of  the  front  face. 

For  the  conventional  representation  of  the  smaller  sizes  it  is 
sufficient  to  draw  the  long  diameter  of  the  head  twice  the  diam- 
eter of  the  shaft,  and  the  thickness  of  both  head  and  nut  equal 
to  the  diameter  of  the  shaft. 

Many  different  lock-nut  devices  to  prevent  nuts  from  working 
loose,  are  used  in  machine  design.  The  jam  nut  or  check  nut  is 
a  common  method,  Fig.  323,  using  either  two  "three-quarters" 
or  standard  nuts,  or  one  full  and  one  thin  nut.  Theoretically 
the  thin  nut  should  be  under,  but  it  is  sometimes  placed  outside. 
D  is  another  application.  In  automobile  work  the  "castle"  nut 
shown  in  Fig.  324  with  pin  through  the  bolt  is  universally  used. 
These  are  made  on  the  A.  L.  A.  M.  (Assn.  of  Licensed  Automobile 
Manufacturers)  standard,  which  has  finer  threads  and  smaller 
heads  and  nuts  than  the  U.  S.  Standard.  A  table  of  sizes  of 
A.  L.  A.  M.  bolts  is  given  under  the  figure. 


WORKING  DRAWINGS 


165 


Cap  screws  differ  from  bolts  in  that  they  are  used  for  fastening 
two  pieces  together  by  passing  through  a  clear  hole  in  one  and 


FIG.  324.— A.  L.  A.  M.  Standard  bolt  and  castle  nut. 


D 

Threads 

A 

B 

c 

E 

F 

H 

K 

L 

i 

28 

I 

$ 

A 

392 

A 

A 

A 

t 

A 

24 

1 

A 

A 

H 

if 

A 

A 

H 

I 

24 

T9<r 

i 

i 

H 

39* 

i 

A 

T^ 

TV 

20 

tt 

1 

i 

H 

H 

i 

A 

H 

* 

20 

t 

i 

A 

A 

1 

i 

A 

f 

T9* 

18 

1 

A 

A 

If 

H 

i 

A 

H 

5 

¥ 

18 

H 

A 

i 

If 

H 

i 

A 

H 

tt 

16 

i 

A 

i 

fi 

If 

i. 

A 

1A 

f 

16 

11 

A 

i 

H 

A 

i- 

A 

H 

1 

14 

H 

A 

i 

If 

H 

1 

A 

1A 

1 

14 

1* 

A 

i 

i 

t 

i 

A 

H 

screwing  into  a  tapped  hole  in  the  other.  The  heads  are  the 
same  thickness  as  the  diameter  of  the  bolt,  but  are  usually 
somewhat  smaller  in  diameter  than  bolt  heads.  Some  cap  screw 


166 


ENGINEERING  DRAWING 


heads  are  made,  however,  to  U.  S.  Standard.     Fig.  325  shows 
six  different  forms  with  an  accompanying  table  of  sizes. 


SQUAP£ 


OVAL  FILLISTER     FLAT  FILL/STEP  BUTTON 

FIG.  325. — Cap  screws. 


COUNTERSUNK 


D 

A 

B 

c 

E 

F 

G 

H 

i 

J 

K 

L 

M 

N 

0 

P 

R 

S 

1 

A 

if 

A 

A 

.032 

3V 

A 

.035 

i 

A 

.040 

A 

A 

i 

A 

A 

A 

.040 

A 

A 

.051 

1 

A 

.064 

A 

1 

I 

A 

ft 

I 

f 

t 

H 

A 

A 

.064 

A 

i 

.072 

if 

A 

.072 

A 

A 

A 

i 

1 

A 

1 

A 

If 

A 

i 

.072 

& 

A' 

.091 

f 

A 

.102 

A 

I 

1 

A 

H 

1 

1 

T9<5 

If 

A 

& 

.091 

f 

A 

.102 

f 

A 

.114 

if 

A 

TV 

f 

if 

T9* 

li 

f 

II 

A 

H 

.102 

1 

3^ 

.114 

if 

A 

.114 

i! 

\ 

i 

I 

U 

f 

li 

f 

it 

i 

T3* 

.114 

if 

i 

.114 

1 

& 

.128 

if 

& 

T96 

if 

i* 

ii 

If 

11 

i* 

6\ 

sV 

.114 

if 

A 

.114 

1 

A 

.133 

A 

1 

I 

i 

ITS<T 

f 

li 

1 

1A 

A 

if 

.128 

i 

T5<r 

.133 

li 

i 

.133 

1! 

1 

I 

i 

H 

1 

if 

1 

li 

T3* 

A 

.133 

U 

t. 

.133 

If 

A 

.133 

A 

1 

I 

li 

Hi 

H 

2i 

H 

1H 

aV 

ft 

.133 

i 

1 

n 

H 

H 

2i 

H 

1A 

i 

t 

.165 

H 

H 

it 

2A 

if 

2f 

* 

H 

H 

li 

2i 

li 

3 

Studs. — Threaded  studs  are  bolts  having  a  thread  on  each  end, 
one  end  to  screw  into  a  tapped  hole,  the  other  for  a  nut,  Fig.  326. 
The  screwed  end  should  be  11/4  to  1  1/2  D  long. 


WORKING  DRAWINGS 


167 


Set  screws  are  used  for  holding  two  parts  in  relative  position, 
being  screwed  through  one  part  and  having  the  point  set  against 
the  other.  They  are  made  with  square  and  hex.  heads,  whose 
thickness  and  short  diameter  are  equal  to  the  diameter  of  the 


FIG.  326.— Studs. 


REGULAR  LOW  HEAD  HEADLESS 

FIG.  327.— Set  screws. 


screw,  with  low  head,  and  headless,  as  shown  in  Fig.  327;  and 
with  points  of  different  shapes  for  different  purposes,  Fig.  328. 
The  Allen  headless  set  screw,  patented  in  1910,  with  countersunk 


POUND         FLAT 


CUP 

FIG.  328.—  Set  screw  points. 


CON£r 


hexagonal  socket,  shown  in  Fig.  330,  is  approved  by  factory 
inspectors  as  safe,  and  is  used  where  there  might  be  danger  of 
clothing  being  caught  in  moving  parts. 


FLAT        POUND    FILLISTER  FRENCH 
FIG.  329. — Machine  screws. 


Machine  screws  are  specified  by  gage  number,  not  by  sizes  in 
fractions  of  an  inch.  Fig.  329  shows  the  various  forms  of 
machine  screw  heads. 


168 


ENGINEERING  DRAWING 


A  new  standard  for  machine  screws  was  proposed  in  1907  by 
the  American  Society  of  Mechanical  Engineers  but  has  not  yet 
come  into  general  use.  Tables  of  these  sizes,  as  well  as  for  other 


ALLEN  HEADLESS 
5ET SCREW 


WOOD  SCREWS 


COLLAR  SCREW 


DRIVE  SCREW. 


LAG  SCREW 


SHOULDER  SCREW 


EXPANSION    BOLT 


HANGER    BOLT 


CARRIAGE   BOLT 


EYE  BOLT 


TURN  BUCKLES 
FIG.  330. — Various  bolts  and  screws. 


WING  NUT 


standard  screws,  may  be  found  in  Kent,  American  Machinist's 

and  other  handbooks. 

Various  other  types  of  bolts  and  screws  are  illustrated  in  Fig.  330. 


F/at  Tops 
F/at  Bottoms 


\F/af  Tops\ 


Complete   Threads 


Pound          Round  Tops  and  Bottoms 
Bottoms  tin*  *T~~    ^  J."na-  /" 


Bottoms 


f  Taper  32  per  f  of  Length 


.8  outside  cf/'am.  +  <4.8 
Threads  V~  Number  o,  Threads  per  /"' 


FIG.  331.  —  Section  of  Briggs  pipe  thread. 


Pipe  Threads  and  Fittings. 

Pipe  threads  are  cut  on  a  taper,  known  as  the  Briggs  Standard, 
illustrated  in  enlarged  scale  in  Fig.  331.  In  drawing  pipes  the 
taper  of  the  threaded  portion  is  usually  slightly  exaggerated. 


WORKING  DRAWINGS  169 

DIMENSIONS  OF  STANDARD  STEEL  AND  WROUGHT  IRON  PIPE. 


Nominal 
inside 
diameter 

Actual 
outside 
diameter 

Actual 
inside 
diameter 

Internal 
area 

Thds. 
per 
inch 

Dist. 
pipe 
enters 

Actual  inside  diam. 

Extra 
heavy 

Double 

extra 

* 

.405 

.270 

.057 

27 

A 

.205 

I 

.540 

.364 

.104 

18 

A 

.294 

1 

.675 

.494 

.191 

18 

U 

.421 

| 

.840 

.623 

.304 

14 

1 

.542 

.244 

I 

1.05 

.824 

533 

14 

H 

.736 

.422 

1 

1.315 

1.048 

.861 

ill 

1 

.951 

.587 

H 

1.66 

1.38 

1.496 

1U 

If 

1.272 

.885 

H 

1.9 

1.61 

2.036 

m 

A 

1.494 

1.088 

2 

2.375 

2.067 

3.356 

111 

11 

1.933 

1.491 

2| 

2.875 

2.468 

4.78 

8 

! 

2.315 

1.755 

3 

3.5 

3.067 

7.383 

8 

i-f 

2.892 

2.284 

3| 

4 

3.548 

9.887 

8 

i 

3.358 

2.716 

4 

4.5 

4.026 

12.73 

8 

1TV 

3.818 

3.136 

4J 

5 

4.508 

15.961 

8 

1A 

4.28 

3.564 

5 

5.563 

5.045 

19.986 

8 

iA 

4.813 

4.063 

6 

6.625 

6.065 

28.89 

8 

H 

5.751 

4.875 

7 

7.625 

7.023 

38.738 

8 

if 

6.625 

5.875 

8 

8.625 

7.982 

50.027 

8 

i* 

7.625 

6.875 

9 

9.625 

8.937 

62.72 

8 

IrV 

8.625 

10 

10.75 

10.019 

78.823 

8 

Itt 

9.75 

170 


ENGINEERING  DRAWING 


Pipe  is  designated  by  the  nominal  inside  diameter,  which 
differs  slightly  from  the  actual  inside  diameter,  as  will  be  noted 
from  the  table  on  page  169.  "  Extra"  and  "double  extra"  heavy 
pipe  has  the  same  outside  diameter  as  standard  weight  pipe  of 
the  'same  nominal  size,  the  added  thickness  being  on  the  inside. 
Thus  the  outside  diameter  of  Vr  pipe  is  1.315,  the  inside  diameter 


S/ZE  OF 

PIPE: 


'A 


73 


I 


M 


'»£ 


*t 


'A 


' 


/O 


4 


a 


FIG.  332.— Cast  iron  fittings. 


of  standard  I"  pipe  1.05,  of  1"  extra  strong  .951,  and  of  XX, 
.587". 

The  dimensions  of  fittings  vary  somewhat  with  the  different 
manufacturers.  In  dimensioning  piping  the  best  practice  is  to 
give  figures  from  center  to  center  of  fittings. 

Fig.  332  illustrates  some  of  the  ordinary  cast  iron  fittings. 
The  dimensions  indicated  are  given  in  the  accompanying  table. 

Fig.  333  shows  malleable  fittings. 


WORKING  DRAWINGS 


171 


deducing  Union 

Coup/mg        /  gfa. 


L-A/Cap  A  ^_ 


A' 


Ji 


I 


~w 


'76 


/xl 


*JL 


FIG.  333. — Malleable  fittings. 


3O   TEETH   -    CAST  Iff  ON   -    FULL  SIZE 
FIG.  334. — Cast  spur  gear. 


172 


ENGINEERING  DRAWING 


/O  P., 48  r. 

DEPTH  OF  CUT.  3/6  " 

FIG.  335. — Cut  spur  gear. 


FIG.  336.— Cast  bevel  gear. 


WORKING  DRAWINGS  173 

Gears. 

While  it  is  not  within  our  scope  to  take  up  any  machine  design, 
it  is  important  that  designers  know  the  correct  methods  for  the 
representation  of  designed  parts.  In  the  working  drawings  of 


5  P/TCfi  -  3S  TEETH 

Finish  a//  o\ser 

FIG.  337— Cut  bevel  gear. 


Ang/e  for  gashing  cuf  5g 

5. 72 "f?D..£ "C. P.  36  TEETH 
HARDENED  STEEL 

FIG.  338. — Worm  and  gear. 


N(<>    Finish  a// over 
"c.P.    S/NGLE  THBEAO 
HARDENED  STEEL 


gears  and  toothed  wheels  the  teeth  are  never  drawn  on  the  wheel. 
For  cast  gears  the  pitch  circle,  addendum  circle  and  root  circle 
are  drawn,  and  the  full  sized  outline  of  one  tooth,  Fig.  334. 


174 


ENGINEERING  DRAWING 


For  cut  gears  the  blank  is  drawn,  and  notes  added  for  full 
information  regarding  pitch,  cutters,  etc.,  Fig.  335. 

Fig.  336  is  a  drawing  of  a  cast  bevel  gear,  showing  the 
method  of  complete  dimensioning  for  the  construction  of  the 
pattern.  Fig.  337  is  a  cut  bevel  gear  and  Fig.  338  is  a  worm 
gear. 

On  assembly  drawings  gears  are  represented  as  in  Fig.  339. 


FIG.  339. 


CONVENTIONAL  SYMBOLS. 

The  methods  of  drawing  screw-threads  and  gears  just  con- 
sidered would  be  called  conventional,  as  they  do  not  represent 
real  outlines  of  the  objects.  Other  conventions  are  used  for 
electrical  apparatus,  for  materials,  etc. 

In  specifying  the  materials  of  which  objects  are  to  be  made, 
the  safest  rule  to  follow  is  to  add  the  name  of  the  material  as  a 
note.  There  are  cases  however  in  which  when  the  piece  is  shown 
in  section,  adjacent  parts  made  of  different  materials  can  be 
indicated  to  good  advantage  by  using  different  characters  of 
cross-hatching. 

The  commonest  example  of  this  is  in  distinguishing  a  bearing 
or  lining  metal  poured  into  place  hot,  such  as  babbitt  metal. 
It  is  universal  practice  to  show  such  metals  by  the  conventional 
symbol  of  crossed  lines  shown  in  Fig.  340.  An  example  of  this 
is  the  lead  lined  valve,  Fig.  144. 


WORKING  DRAWINGS 


175 


The  quickest  way  to  make  this  symbol  is  to  section  over  both 
the  lining  metal  and  the  adjacent  cast  iron  at  once,  then  cross 
the  lining  metal  in  the  other  direction. 

There  have  been  a  number  of  different  codes  of  symbols  pro- 
posed and  published  for  the  representation  on  working  drawings 
of  different  metals  and  materials.  Aside  from  their  doubtful 
value  on  account  of  the  lack  of  agreement,  they  are  all  open  to 
the  same  objection,  that  of  the  added  time  necessary  for  their 
execution. 

With  the  variety  of  materials  used  in  modern  construction  it 
is  entirely  impracticable  to  have  symbols  for  all. 


LEATHER 

(OTHER  FLEXIBLE  MATERIALS) 


GLASS  LIQUID 

FIG.  340. — Symbols  for  materials  in  section. 


INSULATING 
MATERIAL 


Fig.  340  gives  conventions  for  a  number  of  different  mate- 
rials. Those  in  the  first  line  are  accepted  by  practically  all  who 
use  conventional  cross-hatching.  There  is  much  variation  in 
the  symbols  proposed  for  the  other  materials  shown.  Those 
given  are  part  of  the  ,codes  of  government  standards  of  the 
Bureau  of  Steam  Engineering  and  the  Bureau  of  Construction 
U.  S.  N.,  who  require  their  use  on  assembly  drawings  submitted 
by  firms  estimating  on  government  work. 

Until  a  standard  is  adopted  universally  it  would  seem  necessary 
to  add  to  a  drawing  made  with  symbolical  section  lining,  a  key 
to  materials,  as  is  done  in  architectural  drawing,  or  else  to  letter 
the  name  of  the  material  on  each  piece,  in  which  case  the  fancy 
section-lining  would  appear  to  be  unnecessary. 


176 


ENGINEERING  DRAWING 


SQUARE  SECTION 


FIG.  341. — Conventional  breaks  and  other  symbols. 


(6)    (M)          |(M) 

}'renL2Zref7f        O.C.5hut. 

e^ijeorM  «%£%* 

lerafor  or  Motor 

6-6    A 


31 


_j4- 

Crossings 


D.  C.  Ser/es         £>.C.  Compound 
Dynamo 


-0- 


Pnase    TwoPnase 

Alternator 


n         TT 


— C[—      — R 

Orcv/t  Breaker 


— AAAAAAA—        — ^AAA^V — 
Resistance  Vanaffi/e 


Converter 


Transformer      /nsfrvment 
I  Transformer 

1 


Jl     Jl 

i  n    11   R;I 

5.^  &/?  ^./? 

^ST:        0  7:  5.^- 


Sw/fches 


FIG.  342. 


'     *Yor5tor    . 

Connection     Connect/on        Connection 


WORKING  DRAWINGS  177 

Fig.  341  shows  a  number  of  conventional  breaks  and  other 
useful  symbols. 

In  making  a  detail  of  a  long  bar  of  uniform  section  there  is 
evidently  no  necessity  for  drawing  its  whole  length.  It  may  be 
shown  much  better  by  breaking  out  a  piece  and  giving  the  length 
in  a  dimension. 

The  crossed  diagonals  are  used  for  two  distinct  purposes,  to 
indicate  position  or  finish  for  a  bearing,  and  to  indicate  a  piece 
square  in  section,  but  are  not  apt  to  be  confused. 

Sheet  metal  and  structural  shapes  in  section  to  small  scale  may 
be  shown  most  effectively  in  solid  black  with  white  spaces  between 
parts. 

Very  short  section-lines  are  best  made  freehand. 

Fig.  342  gives  a  set  of  electrical  diagrammatic  symbols. 
There  is  no  universal  standard,  but  of  those  proposed  here  a 
number  are  in  general  use.  The  standard  wiring  symbols  of  the 
National  Electrical  Contractors  Association  is  given  on  page  221. 

COMMERCIAL  SIZES. 

The  following  notes  give  the  commercial  methods  of  specifying 
sizes  of  the  items  in  the  list.  The  material  must,  of  course, 
always  be  specified. 

Chain. — Give  diameter  of  rod  used. 

Electrical  Conduit. — Same  as  pipe. 

Pipe. — Give  nominal  inside  diameter. 

R.  R.  Rails. — Give  height  of  section  and  weight  per  yard. 

Rolled  Steel  Shapes; — Give  name,  essential  dimensions  and 
weight  per  foot. 

Rope. — Give  largest  diameter. 

Shafting. — The  best  practice  is  to  give  the  actual  diameter. 

Sheet  Metal. — Give  thickness  by  gage  number,  or  in  thou- 
sandths of  an  inch  (for  3/ 16"  and  over,  give  thickness  in  fractions). 

Springs. — Helical,  give  outside  diameter,  gage  of  wire,  and 
coils  per  inch  when  free. 

Tapered  Pieces. — Give  size  at  small  end,  and  taper  per  foot. 

Tubing. — Give  outside  diameter  and  thickness. 

Wire. — Give  diameter  by  gage  number  or  in  thousandths  of 
an  inch. 

Wire  Cloth. — Give  number  of  meshes  per  lineal  inch,  and  gage 
of  wire. 
12 


178  ENGINEERING  DRAWING 

Wood  Screws. — Give  length,  diameter  by  number,  and  kind  of 
head. 

Special. — Manufactured  articles  or  fittings,  give  manufacturer's 
name  and  catalogue  number. 

CHECKING. 

Before  being  sent  to  the  shop,  a  working  drawing  must  be 
checked  for  errors  and  omissions  by  an  experienced  checker,  who 
in  signing  his  name  to  it  becomes  responsible  for  any  inaccuracy. 
This  is  the  final  "proof-reading"  and  cannot  be  done  by  the  one 
who  has  made  the  drawing  nearly  so  well  as  by  another  person. 
In  small  offices  all  the  work  is  checked  by  the  chief  draftsman, 
and  draftsmen  sometimes  check  each  other's  work;  in  large 
drafting  rooms  one  or  more  checkers  who  devote  all  their  time 
to  this  kind  of  work  are  employed. 

Students  may  gain  experience  in  this  work  by  being  assigned 
to  check  other  students'  work. 

To  be  effective,  checking  must  be  done  in  an  absolutely 
systematic  way,  and  with  thorough  concentration. 

Professor  Follows  in  his  "Dictionary  of  Mechanical  Drawing" 
has  specified  admirably  the  work  of  checking,  in  twelve  items, 
which  are  given  with  his  permission.  Each  of  these  should  be 
followed  through  separately,  allowing  nothing  to  distract  the 
attention  from  it.  As  each  dimension  or  feature  is  verified  a 
checkmark  should  be  placed  above  it. 

1.  Put  yourself  in  the  position  of  those  who  are  to  read  the 
drawing  and  find  out  if  it  is  easy  to  read  and  tells  a 
straight  story.  Always  do  this  before  checking  any 
individual  features;  in  other  words,  before  you  have 
had  time  to  become  accustomed  to  the  contents. 

2.  See  that  each  piece  is  correctly  illustrated  and  that  all 

necessary   views   are   shown,    but   none   that   are   not 
necessary. 

3.  Check  all  the  dimensions  by  scaling,  and,  where  advisable, 

by  calculation  also. 

4.  See  that  dimensions  for  the  shop  are  given  as  required  by 

the  shop,  that  is,  that  the  shop  is  not  left  to  do  any 
adding  or  subtracting  in  order  to  get  a  needed  dimension. 


WORKING  DRAWINGS  179 

5.  Go  over  each  piece  and  see  that  finishes  are  properly 

specified. 

6.  See  that  every  specification  of  material  is  correct  and  that 

all  necessary  ones  are  given. 

7.  Look  out  for  "  interferences."     This  means  check  each 

detail  with  the  parts  that  will  be  adjacent  to  it  in  the 
assembled  machine  and  see  that  proper  clearances  have 
been  allowed. 

8.  When  checking  for  clearances  in  connection  with  a  mechan- 

ical movement,  lay  out  the  movement  to  scale,  figure 
the  principal  angles  of  motion  and  see  that  proper 
clearances  are  maintained  in  all  positions. 

9.  See  that  all  the  small  details,  as  screws,  bolts,  pins,  keys, 

rivets,  etc.,  are  standard  and  that,  where  possible,  stock 
sizes  have  been  used. 

10.  Check  every  feature  of  the  record  strip. 

11.  Review  the  drawing  in  its  entirety  in  connection  with  any 

points  that  rj/ave  suggested  themselves  during  the  above 
checking,  f 

12.  Bearing  in  mind  the  value  of  explanatory  notes,  do  not 

fail  to  add  such  notes  as  your  experience  tells  you  will 
increase  the  efficiency  of  the  drawing. 


STRUCTURAL  DRAWING. 

The  term  "structural  drawing"  is  always  understood  to  mean 
working  drawings  and  details  for  steel  construction,  such  as 
bridges,  roof  trusses,  skeletons  of  tall  buildings,  etc. 

Structural  work  differs  from  machine  work  in  that  it  is  made 
up  of  rolled  shapes  and  put  together  permanently  with  rivets. 
The  function  of  the  drawing  is  to  show  the  shapes  and  sizes  of 
the  steel  used  in  the  design,  and  the  spacing  of  the  rivets. 

Some  of  the  parts  are  put  together  in  the  shop  and  some  at 
the  place  of  erection,  and  a  distinction  must  be  shown  between 
"shop  rivets"  and  "field  rivets."  The  holes  left  for  field  con- 
nection are  always  made  solid  black. 

Fig.  343  shows  the  Osborn  symbols  for  riveting,  which  are 
so  universally  used  that  no  key  on  the  drawing  is  necessary;  and 
Fig.  344  shows  rivets  in  larger  scale. 


180 


ENGINEERING  DRAWING 


In  drawing  rivets  the  drop  pen,  Fig.  30,  is  a  favorite  instrument 
with  structural  draftsmen. 

The  general  rules  for  working  drawings  are  of  course  applicable 
to  this  branch,  but  there  are  some  minor  differences  in  common 
practice  that  should  be  noticed. 


Srtopff/wte 


FIG.  343. — Standard  symbols  for  riveting. 


Structural  drawings  are  necessarily  made  with  finer  outlines 
than  machine  drawings,  and  shade  lines  are  never  used. 

To  prevent  confusion  on  the  tracing,  center  lines  and  gage 
lines  are  very  often  drawn  in  red. 


FIG.  344. 


On  account  of  the  limited  space  for  successive  dimensions,  the 
figures  are  set  over  continuous  dimension  lines,  instead  of  in 
spaces  left  in  the  lines. 

Dimensions  ovbr  one  foot  are  given  in  feet  and  inches. 


WORKING  DRAWINGS  181 

Care  should  be  taken  that  dimensions  are  given  to  commercial 
sizes  of  materials. 

Angles,  as  for  gussets,  are  indicated  by  their  tangent,  on  a  12" 
base  line. 

The  stress  diagram  is  often  added  to  the  drawing. 

Bent  plates  should  be  developed,  and  the  " stretchout"  length 
of  bent  forged  bars  given. 

When  showing  only  part  of  a  given  piece,  always  draw  it  from 
the  left  end  toward  the  right. 

A  bill  of  material  always  accompanies  a  structural  drawing. 
This  may  be  put  on  the  drawing,  but  the  best  practice  now 
attaches  it  as  a  separate  "bill  sheet." 

Figs.  345  and  346  are  given  to  illustrate  the  general  make-up 
of  structural  drawings.  The  original  drawings  were  24"x36". 
When  a  view  is  given  under  a  front  view,  as  in  Fig.  345,  it  is  not 
a  bottom  view,  but  a  section  taken  through  the  web,  above  the 
lower  flange. 

PROBLEMS. 

The  first  part  of  any  working  drawing  problem  consists  of 
the  selection  of  views,  the  choice  of  suitable  scales,  and  the 
arrangement  of  the  sheet.  In  class  work  the  preliminary  sketch 
layout  should  be  submitted  for  approval  before  the  drawing  is 
commenced. 

All  views  of  an  object  must  be  drawn  to  the  same  scale,  but 
different  objects  on  the  same  sheet  may  be  drawn  to  different 
scales. 

The  problems  here  given  may  be  drawn  on  12"xl8"  or  18"x24" 
sheets.  Their  division  into  groups  is  suggestive  rather  than 
arbitrary,  and  the  selections  made  from  them  will  depend 
upon  the  kind  and  length  of  course. 

Group  I. — Bolts,  Screws,  Pipes,  etc. 

Prob.  1. — Draw  helical  screw  threads  and  springs  as  indi- 
cated in  Fig.  347. 

Prob.  2. — Draw  a  bolt  sheet  containing:  3/4"x3"  bolt  with 
hex.  head  and  nut;  3/4"x3"  square  head  bolt;  7/8" 
x3  1/2"  stud,  with  hex.  nut;  l/2"x2"  hex.  head 
cap  screw;  5/8"xl  1/2"  cup  point  set  screw; 


182 


ENGINEERING  DRAWING 


WORKING  DRAWINGS 


183 


184 


ENGINEERING  DRAWING 
Prob.  2.  —  l/4"xl   1/2"  oval   fillister  head   machine   screw; 

(Continued.) 


l/2"x2  1/2"  low  head,  round  point  set  screw,  with 
jam  nut;  5/16"x3/4"  headless  set  screw,  with. 
hanger  point;  3/8"xl  1/2"  countersunk  head  cap 
screw;  l/4"xl  3/4"  round  head  machine  screw; 
3  1/2"  lag  screw  (1/2"  diam,);  2  1/2"  flat  head 


FIG.  347. 

wood  screw  (3/16"  diam.);  l/2"x4"  hanger  bolt, 
with  lock  nut;  5/8"  Allen  set  screw;  1/4"  wing 
nut. 

Prob.  3. — Pipe  Fittings.  In  the  upper  left-hand  corner  of 
sheet  draw  a  2"  T.  Plug  one  outlet,  in  another 
place  a  1  l/2"x2"  bushing,  in  remaining  outlet 
use  a  2"  close  nipple  and  on  it  screw  a  1  l/2"x2" 
reducing  bushing.  Lay  out  remainder  of  sheet  so 
as  to  include  the  following  1  1/2"  fittings:  coup- 
ling, globe  valve,  R.  &  L.  coupling,  angle  valve,  45- 
degree  ell,  90-degree  ell,  45-degree  Y,  cross,  cap,  3 
part  union,  flange  union. 

Add  extra  pipe,  nipples  and  fittings  so  that  the 
system  will  close  at  the  reducing  fitting  first 
drawn. 


WORKING  DRAWINGS 


185 


Prob.  4. — A  Piping  Problem.  Given  two  sources  of  pres- 
sure supply — a  city  main  and  a  steam  pump.  A 
sprinkler  system  must  have  pressure  on  at  all 
times,  and  is  to  be  connected  so  as  to  have  city 
pressure,  pump  pressure,  or  pressure  from  -an 
overhead  tank.  A  battery  of  boilers  is  also  to  be 
connected  to  these  three  sources.  The  tank  is  to 
be  capable  of  supply  from  either  pump  or  main. 


FIG.  348. 


Design  a  pipe  layout  in  elevation,  so  that  each 
system  can  be  operated  independently,  and  be 
perfectly  interchangeable,  using  the  fewest 
fittings  and  simplest  connections.  Fig.  348  is  a 
sketch  showing  the  position  of  the  outlets. 

Group  II. — Study  Sheets  in  Dimensioning. 

(All  to  be  in  orthographic  projection,  with 
necessary  views.) 

Prob.  1. — Make  a  freehand  working  sketch  of  the  casting, 
Fig.  349,  showing  the  location  of  all  dimensions, 
according  to  the  rules  for  dimensioning,  thus 

Prob.  2.— Same  for  Fig.  350. 


186  ENGINEERING  DRAWING 

Prob.  3. — Freehand  sketch  of  yoke  (A)  Fig.  351,  indicating 
dimensions  for  the  blacksmith.  The  holes  to  be 
punched. 

Prob.  4. — Same  for  equalizing  bar  (B)  Fig.  351. 


FIG.  340. 


FIG.  350. 


Prob.  5. — Freehand    sketch    of    casting,    Fig.    352,    giving 

necessary  machine  shop  dimensions  in  blank. 
Prob.  6.— Same  for  Fig.  353. 

Additional  practice  may  be  had  by  applying  the  rules  for 
dimensioning  to  Figs.  130,  140,  294,  295,  296,  etc. 


FIG.  351. 


Group  III. — Drawing  from  Sketches. 

Models,  furnished  by  the  Department,  are  to  be  sketched 
and  measured;  drawings  are  to  be  made  from  the  sketches 


FIG.  352. 


without  further  reference  to  the  model  or  machine;  sketches 
to  be  submitted  along  with  finished  tracings. 
Reference,  Chapter  X,  Technical  Sketching. 


WORKING  DRAWINGS 


187 


Group  IV. — Machine  Parts,  etc. 

Prob.   1. — Make  working  drawing  of  crank  shaft  from  dimen- 
sioned sketch,  Fig.  354. 

Prob.  2. — Working  drawing  of  cross-head,  Fig.  355. 

(Notice  the  occurrence  of  a  curve  of  intersection.) 


FIG.  354. 


FIG.  355. 


Prob.  3. — Working  drawing  of  a  flange  coupling,  size  to  be 
assigned,  and  dimensions  taken  from  the  table 
accompanying  Fig.  356. 

Prob.  4. — Working  drawing  of  bearing,  from  Fig.  357. 


188 


ENGINEERING  DRAWING 

D 


ABC 


UL 


It 


9      4. 


E 


a? 


ZF 


A' 


7J 


FIG.  356. 


ABC 


//f 


3%    4-      8 


M. 


7J7 


FIG.  357. 


WORKING  DRAWINGS 


189 


FIG.  359. 


190 


ENGINEERING  DRAWING 


T     sis 


Section  on  A  A 
FIG.  360. 


Column  5ecf ion    ABC       D      E      F~      O 


H 


L 


22" 


jj. 

/6 


22" 


26 


7" 


24" 


28 


7" 


/P 


¥ 


28"    33"     8"     /e" 


* 


20 


FIG.  361. 


WORKING  DRAWINGS 


191 


FIG.  362. 


FIG.  363. 


192 


ENGINEERING  DRAWING 


WORKING  DRAWINGS 


193 


Prob.  5. — Working  drawing  of  fly-wheel.  Outside  diameter 
60";  hub  6"  diameter,  bore  3",  keyway  l/2"x7/8". 
Arms  at  rim  to  be  3/4  the  size  at  the  hub.  Sec- 
tions of  rim,  arm,  and  hub  are  shown  in  the 
sketch,  Fig.  358. 

Prob.  6. — Working  drawing  of  eccentric,  from  Fig.  359. 

Prob.  7. — Working  drawing  of  pulley,  figuring  dimensions 
from  formulae  given,  Fig.  360. 


FIG.  366. 


Suggested  sizes  (a)  24"  dia.    6"  face  2"  bore. 

(b)  42"  dia.  14"  face  3  7/16"  bore. 

(c)  20"  dia.  10"  face  2  3/16" bore. 

(d)  12"  dia.  16"  face  2  7/16"  bore. 

(e)  60"  dia.    8"  face  3  15/16"  bore. 

(f)  36"  dia.    4"  face  1  7/16"  bore. 

Prob.     8. — Working  drawing  of  column  base,  from  Fig.  361. 
Prob.     9. — Working  drawing  of   a   column  base  with  G  = 

71/2"  and H  =  10",  to  carry  137,000 Ibs.,  assuming 
13 


194 


ENGINEERING  DRAWING 


WORKING  DRAWINGS 


195 


the  bearing  value  of  foundation  to  be  300  Ibs. 

per  sq.  in.     Ribs  45  degrees. 
Prob.   10. — Working  drawing  of  roof  truss  from  sketch,  Fig. 

362. 
Prob.   11. — Working  drawing  of   cast  iron  manhole  cover, 

from  sketch,  Fig.  363. 
Prob.   12. — Working  drawing  of  timber  trestle,  height,  12, 14, 

16,   18,   or   20   feet,   Fig.  364,  using  timbers  of 

sizes  given. 


FIG.  368. 

Group  V. — -Assembly  and  Detail  Drawings. 

Prob.  1. — Make  detail  drawings  of  screw  jack,  Fig.  365. 
Prob.  2. — Make  detail  drawings  of  wrought  iron  hanger, 

Fig.  366. 
Prob.  3. — Make  assembly  drawing  of  milling  machine  vise 

from  details  in  Fig.  367.     The  sketch  is  not  a 

part  of  the  detail  drawing  but  is  given  to  show 

the  arrangement  of  parts. 
Prob.  4. — Make  assembly  and  detail  drawings  of  pop  safety 

valve  from  the  sketch  details  of  Fig.  368. 


196 


ENGINEERING  DRAWING 


IS 


rt.rw    =5  ^^  •> •      v  .  c\  ^0  S*  I  - f       f/M^ 


gj^||i^^j|to 


;/^_j 


WORKING  DRAWINGS 


197 


Prob.  5. — Make  assembly  drawing  of  center  grinder,  from 

detail  drawing,  Fig.  369. 
Prob.  6. — Make  assembly  drawing  of  friction  clutch  shifter, 

from  detail  drawing,  Fig.  308.     Its  arrangement 

is  shown  in  sketch,  Fig.  370. 


FIG.  370. 

Prob.  7. — Make  detail  drawings  of  grinder,  from  assembly 

drawing,  Fig.  371. 
Prob.  8. — Make  assembly  drawing  of  gas  engine  mixer  from 

details  of  Fig.  372. 

Group  VI. — Checking. 

Prob.  1. — Fig.  373  is  incorrect  in  several  places  both  in 
drawing  and  dimensions.  Check  it  for  errors, 
following  the  system  given  on  page  178,  and  re- 
port the  errors  and  corrections  on  a  separate 
sheet. 

Prob.  2. — Check  Fig.  374  in  the  same  way. 

Group  VIII. — Miscellaneous. 

Prob.  1. — A  patent  office  drawing,  on  Bristol  board,  from  an 
assigned  model  or  sketch.  Reference,  Chapter 
XIV. 


198 


ENGINEERING  DRAWING 


WORKING  DRAWINGS 


199 


M/xer  £/eeve 
C0sf/rv/i 


FIG.  372. 


FIG.  373. — An  incorrect  drawing  to  be  checked  for  errors. 


200  ENGINEERING  DRAWING 

Prob.  2. — A  sheet  metal  problem,  to  be  drawn,  developed 
and  dimensioned,  from  specifications  assigned. 

Prob.  3. — A  plan  of  building  or  room,  to  be  measured  and 
drawn.  Reference,  Chapter  XI. 

Prob.  4. — A  problem  in  furniture  designing. 

Prob.  5. — A  problem  in  structural  drawing. 


FIG.  374. — An  incorrect  drawing  to  be  checked  for  errors. 


CHAPTER  X. 

TECHNICAL  SKETCHING. 

From  its  long  use  in  connection  with  art  the  word  "sketch" 
has  come  to  suggest  the  impression  of  a  free  or  incomplete  or 
careless  rendering  of  some  idea,  or  some  mere  note  or  suggestion 
for  future  use.  This  meaning  is  entirely  misleading  and  wrong 
in  the  technical  use  of  the  word.  A  sketch  is  simply  a  working 
drawing  made  freehand,  without  instruments,  the  quick  expres- 
sion of  graphic  language,  but  in  information  adequate  and 
complete. 

So  necessary  to  the  engineer  is  the  training  in  freehand  sketch- 
ing, it  might  almost  be  said  in  regard  to  its  importance  that  the 
preceding  nine  chapters  have  all  been  in  preparation  for  this  one. 
Such  routine  men  as  tracers  and  detailers  may  get  along  with 
skin  and  speed  in  mechanical  drawing,  but  the  designer  must -be 
able  to  sketch  his  ideas  with  a  sure  hand  and  clear  judgment. 
In  all  mechanical  thinking  in  invention,  all  preliminary  designing, 
all  explanation  and  instructions  to  draftsmen  freehand  sketching 
is  the  mode  of  expression. 

It  represents  the  mastery  of  the  language,  gained,  only  after 
full  proficiency  in  mechanical  execution,  and  is  the  mastery  which 
the  engineer,  and  inventor,  designer,  chief  draftsman,  and  contrac- 
tor, with  all  of  whom  time  is  too  valuable  to  spend  in  mechanical 
execution,  must  have. 

It  may  be  necessary  to  go  a  long  distance  from  the  drawing 
room  to  get  some  preliminary  information  and  the  record  thus 
obtained  would  be  valueless  if  any  detail  were  missing  or  obscure. 
Mistakes  or  omissions  that  would  be  discovered  quickly  in  making 
an  accurate  scale  drawing  may  easily  be  overlooked  in  a  freehand 
sketch,  and  constant  care  must  be  observed  to  prevent  their 
occurrence. 

Sometimes,  if  a  piece  is  to  be  made  but  once  a  sketch  is  used 
as  a  working  drawing  and  afterward  filed. 

The  best  preliminary  training  for'  this  work  is  the  drawing  in 

201 


202 


ENGINEERING  DRAWING 


the  public  schools,  training  the  hand  and  eye  to  see  and  represent 
form  and  proportion.  Those  who  have  not  had  this  preparation 
should  practice  drawing  lines  with  the  pencil,  until  the  hand 
obeys  the  eye  to  a  reasonable  extent. 

The  pencil  should  be  held  with  freedom,  not  close  to  the  point, 


FIG.  375. — Sketching  a  vertical  line. 


FIG.  376. — Sketching  a  horizontal  line. 

vertical  lines  drawn  downward,  Fig.  375,  and  horizontal  lines 
from  left  to  right,  Fig.  376. 

An  H  or  2H  pencil  sharpened  to  a  long  conical  point,  not  too 
sharp,  a  pencil  eraser,  to  be  used  sparingly,  and  paper,  either  in 
note  book,  pad,  or  single  sheet  clipped  on  a  board,  are  all, the 
materials  needed. 


TECHNICAL  SKETCHING  203 

In  making  working  sketches  from  objects  a  two-foot  rule  and 
calipers  are  necessary.  Other  machinists'  tools,  a  try  square, 
surface  gauge,  depth  gauge,  thread  gauge,  etc.,  are  very  con- 
venient. The  draftsman's  triangle  may  often  be  used  in  place  of 
a  square.  Sometimes  a  plumb  line  is  of  service.  Much  ingenuity 
is  often  required  to  get  dimensions  from  an  existing  machine. 

Sketches  are  made  in  orthographic,  axonometric,  or  perspective 
drawing,  depending  upon  the  use  which  is  to  be  made  of  them. 
Sketches  of  machine  parts  to  be  used  in  making  working  drawings, 
etc.,  would  be  made  in  orthographic;  explanatory,  or  illustrative 
sketches  might  be  made  in  axonometric  or  perspective. 

The  best  practice  is  obtained  by  sketching  from  castings, 
machine  parts,  or  simple  machines,  and  making  working  draw- 
ings from  the  sketches  without  further  reference  to  the  ob j  ect .  In 
class  work  a  variation  may  be  introduced  by  exchanging  the 
sketches  so  that  the  working  drawing  is  made  by  another  student. 
This  emphasizes  the  necessity  of  putting  down  all  the  information 
necessary,  and  not  relying  on  memory  to  supply  that  missing;  and 
working  with  the  idea  that  the  object  is  not  to  be  seen  after  the 
sketch  is  made.  A  most  valuable  training  in  the  observation  of 
details  is  the  sketching  from  memory  a  piece  previously  studied. 
It  is  an  excellent  training  in  sureness  of  touch  to  make  sketches 
directly  in  ink,  perhaps  with  fountain  pen. 


,*•! 


rv^ 


FIG.  377. 

Sketching  in  Orthographic  Projection. 

The  principles  of  projection  and  all  the  rules  for  working 
drawings  are  to  be  remembered  and  applied  here. 

The  object  should  be  studied  and  the  necessary  views  decided 
upon.  In  some  cases  fewer  views  would  be  made  in  the  sketch 
than  in  the  working  drawing,  as  a  note  in  regard  to  thickness  or 
shape  of  section  might  save  a  view,  Fig.  377.  In  other  cases 


204  ENGINEERING  DRAWING 

additional  views  may  be  sketched  rather  than  complicate  the 
figures  by  added  lines  which  would  confuse  a  sketch,  although 
the  same  lines  might  be  perfectly  legible  in  a  scale  drawing. 

In  beginning  a  sketch  always  start  with  center  lines  or  datum 
lines,  and  remember  that  the  view  showing  the  contour  or  charac- 
teristic shape  is  to  be  drawn  first.  This  is  generally  the  view 
showing  circles  if  there  are  any. 

In  drawing  on  plain  paper,  the  location  of  the  principal  points, 
centers,  etc.,  should  be  marked  so  that  the  sketches  will  fit  the 
sheet,  and  the  whole  sketch  with  as  many  views,  sections  and 
auxiliary  views  as  are  necessary  to  describe  the  piece,  drawn 
without  taking  any  measurements,  but  in  as  nearly  correct  propor- 
tion as  the  eye  can  determine. 

An  object  should  of  course  be  represented  right  side  up,  i.e., 
in  its  natural  working  position.  If  symmetrical  about  an  axis, 
often  one-half  only  need  be  sketched.  Circles  may  be  drawn 
with  some  accuracy  by  marking  on  the  center  lines  points  equi- 
distant from  the  center. 

Often  fragmentary  auxiliary  views  or  sections  aid  in  explaining 
construction.  The  rules  of  projection  are  to  be  broken  if  any 
advantage  may  be  gained. 

If  a  whole  view  cannot  be  made  on  one  page  it  may  be  put  on 
two,  each  being  drawn  up  to  a  break  line  used  as  a  datum  line. 

Sketches  should  be  made  entirely  freehand,  no  ruled  lines  being 
used. 

Dimension  Lines. 

After  the  sketching  of  the  piece  is  entirely  finished  it  should  be 
gone  over  and  dimension  lines  for  all  the  dimensions  needed  for 
the  construction  added,  drawing  extension  lines  and  arrow  heads 
carefully  and  checking  to  see  that  none  are  omitted,  but  still 
making  no  measurements. 

Dimensions. 

Up  to  this  stage  the  object  has  not  been  handled  and  the 
drawing  has  been  kept  clean.  The  measurements  for  the 
dimensions  indicated  on  the  drawing  may  now  be  added.  The 
two-foot  rule  will  serve  for  most  dimensions.  Never  use  the 
draftsman's  scale  for  measuring  castings.  Its  edge  will  be 
marred  and  it  will  be  soiled.  The  diameters  of  holes  may  be 
measured  with  the  inside  calipers.  It  is  often  necessary  to  lay 


TECHNICAL  SKETCHING 


205 


a  straight  edge  across  a  surface  as  in  Fig.  378.  In  measuring  the 
distance  between  centers  of  two  holes  of  the  same  size  measure 
from  edge  to  corresponding  edge.  Always  measure  from  finished 
surfaces  if  possible.  Judgment  must  be  exercised  in  measuring 
rough  castings  so  as  not  to  record  inequalities  due  to  the  foundry. 
Fig.  379  illustrates  measuring  a  curve  by  offsets. 


FIG.  378. 


It  is  better  to  have  too  many  dimensions  rather  than  too  few. 
It  is  a  traditional  mistake  of  the  beginner  to  omit  a  vital  figure. 

Add  all  remarks  and  notes  that  may  seem  to  be  of  any  value 
at  all. 


FIG.  379. — Measurements  by  offsets. 

The  title  should  be  written  on  the  sketch,  and  for  class  sketches 
the  amount  of  time  spent. 

Always  date  every  sketch.  Valuable  inventions  have  been  lost 
through  the  inability  to  prove  priority,  because  the  first  sketches 
had  not  been  dated.  In  commercial  work  the  draftsman's  note- 
book with  its  sketches  and  calculations  is  preserved  as  a  permanent 


206 


ENGINEERING  DRAWING 


record,  and  sketches  should  be  made  so  as  to  stand  the  test  of 

time,  and  be  legible  after  the  details  of  their  making  have  been 

forgotten. 

Cross  Section  Paper. 

Sketches  are  often  made  on  coordinate  paper  ruled  faintly  in 
sixteenths,  eighths  or  quarter  inches,  either  simply  as  an  aid  in 
drawing  straight  lines  and  judging  proportions;  or  assigning 


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-H-i-rT-rH-H— f-j-t-i-f-a-t-^  i-  -i--1-  --;-,-  ^^-H-H-H^-f-^-FW5- 
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FIG.  380.— Sketch  on  coordinate  paper. 

suitable  values  to  the  unit  spaces,  and  drawing  to  approximate 
scale.  In  the  latter  case  a  sufficient  number  of  measurements 
must  be  taken  while  the  sketch  is  being  made,  to  permit  of  its 
being  laid  off  on  the  coordinate  paper.  Fig.  380  is  an  illustration. 

Sketching  by  Pictorial  Methods. 

An  axonometric,  oblique  or  perspective  sketch  of  an  object  or 
of  some  detail  of  construction  will  often  explain  it  when  the 
orthographic  projection  cannot  be  read  intelligently  by  a  work- 
man. Often  again  a  pictorial  sketch  may  be  made  more  quickly 
and  serve  as  a  better  record  than  orthographic  views  of  the  same 
piece  would  do,  and  the  draftsman  who  can  make  a  pictorial 
sketch  with  facility  will  find  abundant  opportunity  for  its 
advantageous  use. 


TECHNICAL  SKETCHING  207 

Axonometric  Sketching. 

Since  measurements  are  not  made  on  sketches  there  is  abso- 
lutely no  advantage  in  sketching  on  isometric  axes  120  degrees 
apart  and  making  an  unnecessary  distortion.  A  much  better 
effect  is  gained  and  the  distortion  greatly  lessened  by  drawing 
the  cross  axes  at  a  much  smaller  angle  with  the  horizontal,  Fig. 
381,  and  foreshortening  them  until  satisfactory  to  the  eye.  It 
is  legitimate  in  such  an  isometric  sketch  still  further  to  decrease 
the  effect  of  distortion  by  slightly  converging  the  receding  lines. 
Objects  of  rectangular  outline  are  best  adapted  to  sketching  in 
axonometric  projection. 


FIG.  381.— 120°  axes  and  flattened  axes  compared. 

When  it  is  important  to  show  the  top  surface  the  axes  may  be 
drawn  at  greater  angles  to  the  horizontal,  and  the  vertical  axis 
foreshortened,  thus  tipping  the  object  forward  as  in  Fig.  382. 

Some  care  must  be  exercised  in  adding  dimensions  to  a  pic- 
torial sketch.  The  extension  lines  must  always  be  either  in  or 
perpendicular  to  the  plane  on  which  the  dimension  is  being  given. 

Oblique  Sketching. 

The  advantage  of  oblique  projection  in  preserving  one  face 
without  distortion  is  of  particular  value  in  sketching,  and  the 
painful  effect  of  this  kind  of  drawing  done  mechanically  may  be 
greatly  lessened  in  sketching,  by  foreshortening  the  cross  axis 
to  a  pleasing  proportion,  Fig.  383.  By  converging  the  lines 
parallel  to  the  cross  axes,  the  effect  of  parallel  perspective  is 
obtained.  This  converging  in  either  isometric  or  oblique  is 
sometimes  called  "fake  perspective." 

Perspective  Sketching. 

A  sketch  made  in  perspective  will  of  course  give  the  best 
effect  pictorially.  As  we  do  not  in  this  book  take  up  the  subject 


208 


ENGINEERING  DRAWING 


of  mechanical  perspective,  with  its  rules  and  methods,  only  the 
phenomena  of  perspective  and  their  application  in  freehand 
sketching  can  be  considered  in  this  connection. 

Perspective  has  already  been  defined  as  being  the  representa- 
tion of  an  object  as  seen  by  the  eye  from  some  particular  station 
point.  Geometrically,  it  is  the  intersection  of  the  cone  of  rays 


FIG.  382. 

from  the  eye  to  the  object,  with  the  vertical  plane,  or  "picture 
plane."  There  is  a  distinction  between  "artist's  perspective" 
and  "geometrical  perspective/'  in  that  the  artist  draws  the 
object  as  he  sees  it  projected  on  the  spherical  surface  of  the 
retina  of  his  eye,  while  geometrical,  or  mechanical  perspective  is 


FIG.  383. — Oblique,  with  and  without  foreshortening. 

projected  on  a  plane,  as  in  a  photograph,  but  except  in  wide 
angles  of  vision  the  difference  is  not  very  noticeable. 

The  ordinary  phenomena  of  perspective,  affecting  everything 
we  see,  the  fact  of  objects  appearing  smaller  in  proportion  to 
their  distance  from  the  eye,  and  of  parallel  lines  appearing  to 
converge  as  they  recede,  are  of  course  well  known. 

The  outline  of  the  object  in  Fig.  384  is  drawn  from  a  photo- 


TECHNICAL  SKETCHING 


209 


graph.  It  will  be  noted  that  the  vertical  lines  remain  vertical 
in  the  picture,  and  that  the  two  sets  of  horizontal  lines  each 
appear  to  converge  toward  a  point  called  the  "  vanishing  point. " 
These  two  vanishing  points  will  lie  on  a  horizontal  line  drawn 
at  the  level  of  the  eye,  called  the  " horizon";  and  the  first  rule  is, 
all  horizontal  lines  vanish  on  the  horizon. 

When  the  object  is  turned  as  in  Fig.  384,  with  its  vertical  faces 
at  an  angle  with  the  picture  plane,  the  drawing  is  said  to  be  in 
angular  perspective.  It  is  sometimes  called  "two-point"  per- 
spective because  of  having  two  vanishing  points. 


FIG.  384. — Perspective  (from  photograph). 

If  the  object  is  turned  so  that  one  face  is  parallel  to  the  picture 
plane,  the  horizontal  lines  on  that  face  and  all  lines  parallel  to 
them  would  remain  horizontal  in  the  picture  and  would  thus 
have  no  vanishing  point.  The  object  drawn  in  this  position  is 
said  to  be  in  parallel,  or  "one-point"  perspective. 

In  sketching  in  perspective  from  the  model  the  drawing  is 
made  simply  by  observation,  the  directions  and  proportionate 
lengths  of  lines  being  estimated  by  sighting  and  measuring  on  the 
pencil  held  at  arm's  length;  and  knowledge  of  the  geometrical 
rules  and  principles  used  only  as  a  check. 

With  the  drawing  board  or  sketch  pad  held  perpendicular  to 
the  "line  of  sight"  from  the  eye  to  the  object,  the  direction  of  a 
line  is  tested  by  holding  the  pencil  at  arm's  length  parallel  to 
the  board,  rotating  the  arm  until  the  pencil  appears  to  coincide 
with  the  line  on  the  model,  then  moving  it  parallel  to  this  position, 
back  to  the  board. 

The  apparent  lengths  of  lines  are  estimated  in  the  same  way, 
holding  the  pencil  in  a  plane  perpendicular  to  the  line  of  sight, 
14 


210  ENGINEERING  DRAWING 

marking  with  the  thumb  the  length  of  pencil  which  covers  a  line 
of  the  model,  rotating  the  arm,  with  the  thumb  held  in  position, 
until  the  pencil  coincides  with  another  line,  and  estimating  the 
proportion  of  this  measurement  to  the  second  line,  Fig.  385. 

The  sketch  should  be  made  lightly,  with  free  sketchy  lines,  and 
no  lines  erased  until  the  whole  sketch  has  been  blocked  in. 

Have  the  drawing  as  large  as  the  paper  will  admit. 

In  constructing  a  perspective  from  an  orthographic  or  other 
drawing,  use  may  be  made  of  the  plan  and  cone  of  rays,  and  the 
vanishing  points.  Imagining  the  eye  as  located  at  the  station 


FIG.  385. 

point,  a  little  thought  will  show  that  the  vanishing  point  of  any 
system  of  parallel  lines  is  the  projection  on  the  picture  plane  of 
their  infinite  ends,  the  eye  looking  farther  and  farther  out,  till 
the  line  of  vision  is  parallel  to  the  lines.  Hence,  the  vanishing 
point  of  any  system  of  parallel  lines  is  found  by  drawing  from  the 
station  point  a  line  parallel  to  the  given  lines  and  finding  where  it 
pierces  the  picture  plane. 

A  line  drawn  from  the  station  point  perpendicular  to  the 
picture  plane  pierces  it  in  a  point  called  the  "center  of  vision." 
Evidently  all  lines  perpendicular  to  the  picture  plane  will  vanish 
in  the  center  of  vision.  This  is  the  basis  of  parallel  perspective. 

An  object  in  parallel  perspective  with  one  face  in  the  picture 
plane  is  shown  at  A,  Fig.  386.  At  B  is  shown  the  top  view  of  A 


TECNHICAL  SKETCHING 


211 


with  the  cone  of  rays.  C  shows  the  picture  plane  detached  and 
set  forward  in  order  that  it  may  not  interfere  with  the  plan  when 
revolved.  D  is  the  top  view  of  C  after  the  picture  plane  has  been 
revolved. 


FIG.  386.— Parallel  perspective. 


FIG.  387. — Angular  perspective. 

It  will  be  noticed  that  the  edges  perpendicular  to  the  picture 
plane  vanish  in  the  center  of  vision,  and  that  their  perspective 
lengths  are  found  by  dropping  to  them  points  the  of  intersection 
of  the  cone  of  rays  with  the  picture  plane. 

Direct  measurements  can  be  made  only  in  the  picture  plane. 


212 


ENGINEERING  DRAWING 


The  station  point  should  be  taken  at  a  distance  at  least  twice 
the  length  of  the  longest  side. 

Fig.  387  is  a  series  illustrating  an  object  in  angular  perspective. 
A  the  object,  with  one  corner  in  the  picture  plane;  B  the  plan, 


FIG.  388. 


showing  the  finding  of  the  vanishing  points  for  the  two  series  of 
horizontal  lines  by  drawing  lines  through  the  station  point  paral- 
lel to  them;  C  the  picture  plane  moved  forward  bringing  with  it 


FIG.  389.— A  perspective  sketch. 

the  horizon  and  vanishing  points;  D  the  picture  plane  revolved. 
The  figure  illustrates  the  general  case.  It  is  usual,  in  practice, 
to  take  the  S.  P.  directly  in  front  of  the  corner  that  is  in  the 
P.P. 


TECHNICAL  SKETCHING 


213 


Fig.  388  shows  that  the  vanishing  point  of  a  system  of  oblique 
lines  is  on  a  perpendicular  from  the  vanishing  point  of  their 
projections. 

Fig.  389  gives  an  application  of  perspective  sketching,  showing 
construction. 

Fig.  390  contains  a  selection  of  perspective  sketches  to  be 
sketched  in  orthographic. 


FIG.  390. — Perspective  sketches. 


CHAPTER  XI. 

THE  ELEMENTS  OF  ARCHITECTURAL  DRAWING. 

It  is  entirely  beyond  the  scope  of  this  book  to  take  up  archi- 
tectural designing.  But  in  the  application  by  the  architect,  of 
engineering  drawing  as  a  language,  there  are  idioms  and  peculi- 
arities of  expression,  with  which  all  engineers  should  be  familiar, 
as  in  the  interrelation  of  the  professions  they  are  often  required 
to  read  or  work  from  architects'  drawings,  or  to  make  the  draw- 
ings for  special  structures. 
Characteristics  of  Architectural  Drawing. 

The  general  principles  of  drawing  are  the  same  for  all  kinds  of 
technical  work.  Each  profession  requires  its  own  special  appli- 
bation  of  these  principles,  and  the  employment  of  particular 
methods,  symbols  and  conventions. 

In  architectural  drawing  the  necessary  smallness  of  scale 
makes  it  impossible  to  represent  the  different  parts  exactly,  and 
the  drawings  thus  become  largely  conventional.  The  necessary 
notes  for  their  explanation,  and  the  information  regarding  the 
details  of  material  and  finish  are  too  extensive  to  be  included  on 
the  drawings  so  are  written  separately,  and  are  called  the  speci- 
fications. These  specifications  have  equal  importance  and 
weight  with  the  drawings. 

Architecture  is  one  of  the  fine  arts,  and  in  an  architect's  draw- 
ings there  is  an  evidence  of  artistic  feeling  in  their  make  up, 
produced  in  part  by  the  freehand  work  and  lettering  upon  them, 
that  gives  them  an  entirely  different  appearance  from  a  set  of 
machine  drawings. 

The  present  day  fad  of  over  running  corners  is  however  a 
rather  senseless  affectation. 
Kinds  of  Drawings. 

Architectural  drawings  may  be  divided  into  three  general 
classes : 

(1)  Display  and  competitive  drawings. 

(2)  Preliminary  sketches. 

(3)  Working  Drawings. 

214 


THE  ELEMENTS  OF  ARCHITECTURAL  DRAWING        215 


216 


ENGINEERING  DRAWING 


THE  ELEMENTS  OF  ARCHITECTURAL  DRAWING        217 


FIG.  393. — Perspective  in  ruled  outline. 


FIG.  394.— A  pencil  rendering. 


218 


ENGINEERING  DRAWING 


FIG.  395. — A  pen  drawing. 


FIG.  396.— A  wash  drawing. 


THE  ELEMENTS  OF  ARCHITECTURAL  DRAWING        219 

Display  Drawings. 

The  object  of  display  drawings  is  to  give  a  realistic  or  effective 
representation  of  the  arrangement  and  appearance  of  a  proposed 
building,  for  illustrative  or  competitive  purposes.  They  may  be 
either  plans  and  elevations,  or  may  include  perspective  drawings; 
and  contain  little  or  no  structural  information.  For  legibility 
and  attractiveness  they  are  "rendered/'  generally  on  Whatman, 
eggshell,  tracing,  or  other  white  paper,  in  some  medium,  giving 
the  effect  of  light  and  shade.  Fig.  391  illustrates  an  elevation 
rendered  in  wash,  in  which  a  certain  perspective  effect  is  added 
by  extending  the  foreground. 

Figures,  trees,  other  buildings,  etc.,  are  sometimes  introduced 
on  such  drawings,  not  so  much  for  pictorial  effect,  but  to  give  an 
idea  of  the  relative  size  of  the  buildings. 

In  rendering  plans  for  display  or  competitive  purposes,  tints 
and  shadows  are  often  used  to  show  the  plan  in  relief  and  to 
express  the  ideas  of  the  architect  more  fully.  Fig.  392  illustrates 
a  plan  of  this  kind,  employing  poche  and  mosaic;  "poche" 
meaning  simply  the  blackening  of  the  walls  to  indicate  their 
relative  importance  in  the  composition,  and  "  mosaic "  the 
rendering,  in  light  lines  and  tints,  of  the  floor  design,  furniture, 
etc.,  on  the  interior,  and  the  walks,  drives  and  gardening  of  the 
exterior. 

The  architect  must  be  familiar  with  perspective  drawing,  as 
he  uses  it  both  in  the  preliminary  study  of  his  problem  and  to 
show  the  client  the  finished  appearance  of  the  proposed  structure. 
Perspectives  are  rendered  according  to  the  purpose  of  the  draw- 
ing. Four  different  methods  are  illustrated.  Fig.  393  is  a  ruled 
outline,  Fig.  394  a  pencil  drawing,  usually  done  on  tracing  paper; 
Fig.  395  a  pen  drawing,  and  Fig.  396  awash  drawing,  done  either 
in  monochrome  or  in  color.  In  rendering  a  perspective  in  water 
color  it  is  best  to  transfer  it  by  rubbing,  as  described  on  page 
268,  in  order  to  preserve  the  surface  of  the  paper. 

Preliminary  Sketching. 

The  architects'  designing  problems  present  so  many  solutions 
that  a  great  amount  of  preliminary  sketching  is  necessary,  and 
the  architectural  draftsman  must  be  facile  with  the  pencil. 
These  schemes  are  carried  on  first  in  very  small  sketches,  not  to 
scale,  and  afterward  worked  up  enlarging  them  in  sketches  to 


220 


ENGINEERING  DRAWING 


scale.  Tracing  paper  is  very  desirable  for  this  work  as  one  sketch 
can  be  made  over  another,  thus  saving  time  in  laying  out,  and 
enabling  the  preservation  of  all  the  different  solutions.  The 
final  preliminary  sketches  are  submitted  to  the  client,  and  should 
give  all  the  general  dimensions.  In  preparing  these  sketches 
the  important  consideration  to  be  kept  in  mind  is  that  the  client 
is  usually  a  person  not  accustomed  to  reading  a  drawing,  and  that 
they  must  therefore  be  particularly  clear  and  free  from  ambiguity. 
Tracing  paper  drawings  are  often  mounted  for  display  either 
by  " tipping"  or  " floating,"  as  described  on  page  267. 

'  AILCH1TECTV1LAL  «  SYMBOLS  - 


•EAfcTHMM'SECTlOrt'  'COflCRETE-lH-SECTIOrt-  >£TA6E5WMAKIN6>CONCRCfE*yM80l 

FIG.  397. — Symbols  for  building  materials. 

Working  Drawings. 

All  the  general  principles  in  Chapter  IX  regarding  working 
drawings  are  applicable  to  architectural  working  drawings. 
The  assembly  drawings  are  plans,  elevations  and  sections.  The 
plans  of  a  building  of  the  size  of  an  ordinary  house  would  be 
drawn  to  the  scale  of  1/4"=  1',  larger  buildings  to  1/8"=  1'. 
In  order  to  keep  the  drawings  to  convenient  working  size,  only 
one  view,  usually,  is  drawn  on  a  sheet. 
Plans. 

A  floor  plan  is  a  horizontal  section  at  a  distance  above  the  floor 
varying  so  as  to  cut  the  walls  at  a  height  which  will  best  show 


THE  ELEMENTS  OF  ARCHITECTURAL  DRAWING        221 


STANDARD    SYMBOLS    FO&  WIRING    PLANS 

OS    adopted  and    recommended    by 
THE  NATIONAL  ELECTRICAL  CONTRACTORS  ASSOCIATION  of  the  UNITED  STATES  and  THE  AMERICAN.  INSTITUTE  of  ARCHITECTS 


Celling  Outlet;    Electric  only.   Numeral 
in   center    indicates     number   of 
Standard    16  C.R    Incandescent  Lamps. 

Bracket  Outlet;    Electric  only.   Numeral^ 
in   center     indicates     number    of 
Standard    16  C.R    Incandescent    Lamps. 

Ceiling  Outlet;   Gas   only. 


m 


Wall  or    Baseboard    Receptacle.  Numeral      > 

in   center     indicates    number  of 

Standard    16  C.P.    Incandescent  Lamps.       < 

f      Outlet  for  Outdoor   Standard    or 

)6  Pedestal;    Electric  only.  Numeral  indicates 

*      number  of  Stand.  16  C.P.  Incan .  Lamps. 

\      Drop   Cord    Outlet. 
|      Arc     Lamp   Outlet. 


Ceiling  Outlet.  Combination  .|  indicate* 

•  4- 16  C.P.  Standard    Incandescent 
Lamps  and     2   Gas     Burners  . 

Bracket    Outlet ;    Combination  . 
^   indicates  4-16  C  P.  Standard   Incan- 
descent   Lamps  and  2  Gas    Burners. 

Bracket  Outlet;   Gas    only. 

Tloor    Outlet       Numeral     irt 
center     indicates     number     of 
Standard    16  C  P    Incandescent  Lamps. 

Outlet  for  Outdoor  Standard  or  Pedestal. 

•  Combination    ^-indicates   6-16  C  P 
Stand  .  Incan.  Lamps  and  6  6as  Burners. 

One    Light  Outlet  for  Lamp  Receptacle. 


Special  Outlet,  for  Lighting  ,  Heating 
and  Power  Current,  as  described  in  Spec. 


S1       S.P.   Switch    Outlet. 
S2-     D.P.  Switch  Outlet. 
S3      3- Way  Switch  Outlet. 
S*     4- Way  Switch  Outlef 

Automatic  Door  Switch  Outlet. 
Electrolier   Switch    Outlet. 
Meter  Outlef. 
Junction  or    Pull    Box  » 
Cx3     Motor    Control    Outlet  . 

'  Main  or  Feeder  run  concealed  under  floor. 

—  —•-   Main  or   Feeder    run  exposed. 


Ceiling    Fan   Outlet. 
\ 


S° 
SE 


Show  as  many   symbols  as    there  are 
switches,  or  ,  in  case  of  a- very   larg*» 
group  of  switches,  indicate  number 
of  switches  by  a    Roman  Numeral  , 
thus  :  S1  XII ,  meaning  12  Single '  Pole 
switches.      Describe   type  of  switch 
in  specifications,   that  is,    Flush  or 
Surface  ,  Push  Button   or  Snap. 

Distribution      Panel  . 

Motor  Outlet:  Mumeral  .o  center  indicates  H.R 

Transformer  . 

•  Mam  or  Feeder  run  concealed  under  floorobo»e. 

•  Branch  Circuit  run  concealed  under  floor. 


Branch  Circuit  run  concealed  under  floor  above. Branch   Circuit   Run  Exposed 

-•• — •"   Pole    Line.  •         Riser. 

fa        Telephone  Outlet,  Private  Service  .     M      Telephone  Outlet;  Public  Service      H      Bell  Outlet. 
f~"V       Buzzer  Outlet.        ]  •  |g    Push  Button   Outlet;  Numeral   Indicates  number-  of    Pushes. 
____/B\ Annunciator:  Humeral    indicates    number  of    Points.  ^      Sp«a)ting     Tub*. 

(S)      Watchman    Clock  Outlet .  — J  Watchman  Station  Outlet.   — -®   Master  Time  Clock  Outlet. 

[[)     Secondary    Ti'me   Clock   Outlet.  GO       Door    Opener 

JXJ        Special  Outlet;    for  Signal   Systems.as  described    in    Specifications.     |l|l||       Battery  Outlet. 

f   Circuit-for  Clock,  Telephone  ,  Bell  or  other  Service,  run  under  floor ,  conccolad. 

""  \  Kind  of   Service    wanted   ascertained   by   Symbol  to  which   line   connects 

-  (  Circuit   for  Clock,  Tele  phone.  Bell  or  other  Service,  run  under  floor  above  concealed. 

\  Kind   of   Service    wanted   ascertained    by   Symbol   to  which   line,   connects. 

Note—  If  other   than   Standard    16  C.R   Incandescent    Lamps    ore.  desired, 
Specifications    should    describe  capacity    of   Lamp  to    be    used 

SUGGESTIONS  IK  COMHECTIOtt    WITH ,  STANDARD    SYMBOLS     TOR.   WllEING     PLANS 

It  i*  important  that  ample   space     bt    allowed    for   the     installation   of    mains,  feeders,  branches  and    distribution 
panels  .      It  is    da.sirable    that  a    key    to    the    symbols    used    accompany    oil    plans. 

If  mains  ,    feeders  ,   branches   and    distribution    panels  ore   shown  on  the    plan*  ,   .it  i*   desirable    that   they 
be    designated    by    letters   or    numbers. 

'       Living    Rooroa  S'-6" 

S'-O" 
6'-0" 
6'- 3' 

41-0- 

F    THE     UNITED     5TATCS- 


Me.ghts  of  center  of    W( 
Outlets  (unless   otherwis 


specified  j 
Height   of  switches  (unless    otherwise 


„,          (       Living    Roo 
Chambers 
}         Off.ce* 
\        Corridor* 


COPYRIGHT  -l«0«    -I9O7       BY    THE     NAT 


FIG.  398. — Standard  wiring  symbols. 


222 


ENGINEERING  DRAWING 


the  construction.  The  cut  would  thus  evidently  cross  all 
openings  no  atmter  at  what  height  they  were  from  the  floor. 
The  joist  system  or  construction  of  the  floor,  and  also  any  infor- 
mation regarding  the  ceiling  above,  as  beams,  gas  and  electric 
outlets,  etc.,  may  be  shown  on  the  same  drawing. 


£•;  -  Ilfadr 

:::-:;;::."5-  ^"TT^ — I- 


FIR.3  7  •  FLOOR..   PLAM  • 

'     »  C  A  L  E  •  «'•  4-0*     • 


HESIDETtCE    • 

/^          ' 

MR.-A-F-  BR.OOKS 

MEDIA    •   OHIO 

X'Y'Z.   •   AR.CHI 

TECT 

DF  CATVR-   •    ILL 

I      ' 

FIG.  399. — A  residence  floor  plan. 

The  different  details  such  as  windows,  doors,  etc.,  must  be 
indicated  by  conventional  representation,  using  symbols,  which 
are  readily  understood  by  the  contractors  who  have  to  read  the 
drawings,  A  wall,  of  whatever  material,  is  shown  by  two  lines 
giving  its  thickness,  with  the  space  between  generally  section- 
lined  (or  tinted)  to  indicate  the  material.  A  code  of  conventional 


THE  ELEMENTS  OF  ARCHITECTURAL  DRAWING        223 


symbols,  representing  good  practice,  is  given  in  Fig.  397.  As 
there  is  no  universally  accepted  standard  of  symbols,  a  key  to 
materials  represented  in  section  should  always  be  shown  on  the 
drawing. 

Fig.  398  contains  the  standard  symbols  for  wiring  plans. 


5E  COM  D   •   FLOO  R_  -  PUAN 

•  s  CA  L  e  •  r-  4-0"  • 


RESIDE  MCE  •/£. 
MR.-A-F.-BR.OOKS 

MEDIA    •    OHIO    « 
X-Y-Z   •   ARCHITECT 
DE  CATVR.  •    ILL  • 


FIG.  400. — A  residence  floor  plan. 

Figs.  399  and  400  are  representative  residence  floor  plans, 
showing  the  application  of  a  number  of  conventions,  and  Fig.  401 
is  the  plan  of  an  engineering  structure. 

Elevations. 

An  elevation  is  a  vertical  projection  showing  the  front,  side  or 
rear  view  of  a  structure,  giving  the  heights  and  exterior  treat- 


224 


ENGINEERING  DRAWING 


FIG.  401. — Floor  plan  of  sub-station. 


FIG.  402.— An  elevation,  with  wall  section. 


THE  ELEMENTS  OF  ARCHITECTURAL  DRAWING        225 

ment.  The  visualizing  power  must  be  exercised  to  imagine  the 
actual  appearance  or  perspective  of  a  building  from  its  elevations. 
Roofs  in  elevation  are  thus  often  misleading  to  persons  unfamiliar 
with  drawing,  as  their  appearance  in  projection  is  so  different 
from  the  real  appearance  of  the  building  when  finished. 

Only  those  dimensions  should  be  put  on  elevations  as  are  not 
possible  to  show  on  the  other  drawings. 

Fig.  402  is  an  elevation,  with  wall  section  of  the  house  whose 
plans  are  shown  in  Figs.  399  and  400. 


FIG.  403.— Section  of  sub-station. 

Sections. 

A  section  is  an  interior  view  on  a  vertical  cutting  plane  and  is 
used  primarily  to  indicate  the  heights  of  the  floors  and  different 
parts,  and  to  show  the  construction  and  architectural  treatment 
of  the  interior.  In  a  simple  structure  a  part  section  or  "wall 


226 


ENGINEERING  DRAWING 


section/'  shown  with  the  elevation,  as  in  Fig.  402,  is  often  suffi- 
cient. This  cutting  plane,  as  the  horizontal,  need  not  be  continu- 
ous, but  may  be  broken  so  as  to  include  as  much  information  as 
possible.  Fig.  403  is  a  full  section,  or  sectional  elevation  of  the 
sub-station  shown  in  plan  in  Fig.  401. 
Details. 

Architectural  details  are  made  to  explain  peculiar  construc- 
tions or  to  give  a  full  graphic  description  of  any  part.     Often 


•  DETAIL -OF-  FRAMING  'AR.QVND    BASE  MEMT'  WIHDOW5  • 
SCALE  £"=i-o" 

FIG.  404. — An  isometric  detail. 

some  peculiarity  of  framing  may  be  explained  easily  by  an  iso- 
metric detail,  as  Fig.  404.  Stair  details  and  the  like  may  be 
shown  with  sufficient  clearness,  as  in  Fig.  405,  to  the  scales  of 
3/4"  or  I".  Mouldings  and  other  mill  work  details  are  generally 
made  full  size.  The  turned  or  revolved  section  is  often  of  use 
in  showing  moulding  sections  in  position. 

Dimensioning. 

As  in  machine  drawing,  the  correct  dimensioning  of  an  archi- 
tectural drawing  requires  a  knowledge  of  the  methods  of  building 


THE  ELEMENTS  OF  ARCHITECTURAL  DRAWING        227 

construction.  The  dimensions  should  be  placed  so  as  to  be  the 
most  convenient  for  the  workman,  should  be  given  from  and  to 
accessible  points,  and  chosen  so  that  commercial  variation  in  the 
sizes  of  materials  will  not  affect  the  general  dimensions. 

A  study  of  the  dimensioning  on  the  figures  of  this  chapter  will 
be  of  value. 

The  statement  that  the  notes  were  put  in  the  specifications 
does  not  at  all  imply  that  no  notes  are  to  be  placed  on  the 


FIG  405. — A  stair  detail. 

drawings.  On  the  other  hand,  there  should  be  on  architectural 
working  drawings  clear,  explicit  notes  in  regard  to  material, 
construction  and  finish.  The  builders  are  apt  to  overlook  a 
point  mentioned  only  in  the  specifications,  but  as  they  are  using 
the  drawings  constantly,  will  be  sure  to  see  a  reference  or  note 
on  the  drawing  of  the  part  in  question. 

Lettering. 

There  are  two  distinct  divisions  in  the  use  of  lettering  by  the 
architect,  the  first,  Office  Lettering,  including  all  the  titles  and 
notes  put  on  drawings  for  information;  the  second,  Design 
Lettering,  covering  drawings  of  letters  to  be  executed  in  stone  or 
bronze  or  other  material  in  connection  with  design. 


228  ENGINEERING  DRAWING 

The  Old  Roman  is  the  architect's  one  general  purpose  letter 
which  serves  him  with  few  exceptions  for  all  his  work  in  both 
divisions.  It  is  a  difficult  letter  to  execute  properly  and  the 
draftsman  should  make  himself  thoroughly  familiar  with  its 
construction,  character,  and  beauty,  through  a  text-book  on 
the  subject,  before  attempting  to  design  inscriptions  for  perma- 
nent structures,  or  even  titles. 

Titles  on  display  drawings  are  usually  made  in  careful  Old 
Roman,  and  on  working  drawing,  in  a  rapid  single  stroke  based 
on  Old  Roman.  For  notes  the  Reinhardt  letter  is  best  adapted. 

An  architectural  title  should  contain  part  or  all  of  the  following 
items: 

(1)  Name  and  location  of  structure. 

(2)  Kind  of  view,  as  roof  plan,  elevation  (sometimes  put  on 
different  part  of  sheet). 

(3)  Name  and  address  of  owner  or  client. 

(4)  Date. 

(5)  Scale. 

(6)  Name  and  address  of  architect. 

(7)  Number  (in  the  set). 

(8)  Key  to  materials. 

(9)  Office  record. 


CHAPTER  XII. 
MAP  AND  TOPOGRAPHICAL  DRAWING. 

Thus  far  in  our  consideration  of  drawing  as  a  graphic  language 
we  have  had  to  represent  the  three  dimensions  of  an  object, 
either  pictorially  or,  in  the  usual  case,  by  drawing  two  or  more 
views  of  it.  In  map  drawing,  the  representation  of  features  on 
parts  of  the  earth's  surface,  there  is  the  distinct  difference  that 
the  drawing  is  complete  in  one  view,  the  third  dimension  (the 
height)  either  being  represented  on  this  view,  or  in  some  cases 
omitted  as  not  required  for  the  particular  purpose  for  which  the 
map  was  made. 

The  surveying  and  mapping  of  the  site  is  the  first  preliminary 
work  in  improvements  and  engineering  projects,  and  it  is  desira- 
ble that  all  engineers  should  be  familiar  with  the  methods  and 
symbols  used  in  this  branch  of  drawing.  Here  again,  as  in  our 
discussion  of  architectural  drawing,  we  cannot  consider  the  prac- 
tice of  surveying  and  plotting,  or  go  into  detail  as  to  the  work  of 
the  civil  engineer,  but  we  are  interested  in  his  use  of  drawing  as 
a  language,  and  in  the  method  of  commercial  execution  of  plats 
and  topographical  maps.  The  titles  of  several  books  on  plane 
and  topographic  surveying  are  given  in  Chapter  XV. 

Maps  in  general  may  be  classified  as  follows: 

(1)  Those  on  which  the  lines  drawn  represent  imaginary  or 
unreal  lines,  such  as  divisions  between  areas  subject  to  different 
authority  or  ownership,  either  public  or  private;  or  lines  indicating 
geometrical  measurements  on  the  ground.     In  this  division  may 
be  included  plats  or  land  maps,  farm  surveys,  city  subdivisions, 
plats  of  mineral  claims. 

(2)  Those   on   which  lines   are   drawn   to   represent   real   or 
material  objects  within  the  limits  of  the  tract,  showing  their 
relative  location,  or  size  and  location,  depending  upon  the  purpose 
of  the  map.     When  relative  location  only  is  required  the  scale 
may  be  small,  and  symbols  employed  to  represent  objects,  as 
houses,  bridges  or  even  towns.     When  the  size  of  the  object  is  an 

15  229 


230  ENGINEERING  DRAWING 

important  consideration  the  scale  must  be  large  and  the  map 
becomes  a  real  orthographic  top  view. 

(3)  Those  on  which  lines  or  symbols  are  drawn  to  tell  the 
relative  elevation  of  the  surface  of  the  ground.  These  would  be 
called  relief  maps,  or  if  contours  are  used  with  elevations  marked 
on  them,  contour  maps. 

Various  combinations  of  these  divisions  may  be  required  for 
different  purposes.  A  topographic  map,  being  a  complete 
description  of  an  area,  would  include  1,  2  and  3,  although  the 
term  may  be  used  for  a  combination  of  any  two. 

Plats. 

A  map  plotted  from  a  plane  survey,  and  having  the  third 
dimension  omitted,  is  called  a  "plat"  or  "land  map."  It  is 
used  in  the  description  of  any  tract  of  land  wrhen  it  is  not  neces- 
sary to  show  relief,  as  in  such  typical  examples  as  a  farm  survey 
or  a  city  plat. 

The  first  principle  to  be  observed  in  the  execution  of  this  kind 
of  drawings  is  simplicity.  Its  information  should  be  clear,  con- 
cise and  direct.  The  lettering  should  be  done  in  single  stroke, 
and  the  north  point  and  border  of  the  simplest  character.  The 
day  of  the  intricate  border  corner,  elaborate  north  point,  and 
ornamental  title  is,  happily,  past,  and  all  such  embellishments 
are  rightly  considered  not  only  as  a  waste  of  time,  but  as  being 
in  extremely  bad  taste. 

A  Farm  Survey. 

The  plat  of  a  farm  survey  should  give  clearly  all  the  informa- 
tion necessary  for  the  legal  description  of  the  parcel  of  land.  It 
should  contain: 

(1)  Lengths  and  bearings  of  the  several  sides. 

(2)  Acreage. 

(3)  Location  and  description  of  monuments  found  and  set. 

(4)  Location  of  highways,  streams,  etc. 

(5)  Official  division  lines  within  the  tract. 

(6)  Names  of  owners  of  abutting  property. 

(7)  Title  and  north  point. 

(8)  Certification. 

Fig.  406  illustrates  the  general  treatment  of  this  kind  of 
drawing.  It  is  almost  always  traced  and  blue  printed,  and  no 


MAP  AND  TOPOGRAPHICAL  DRAWING 


231 


water  lining  of  streams  or  other  elaboration  should  be  attempted. 
It  is  important  to  observe  that  the  size  of  the  lettering  used  for 
the  several  features  must  be  in  proportion  to  their  importance 


/ 


/  '  frereby  certify  ffre  atove  p/0f  /{?  be  correct 


PLAT 
OF svxYfr of 

TH£J.  C.WARD  FARM 

Z.OT6  TffACTfZ  Oit.OT-9-  TKACT8 

MAD/SOM  THSf>. 
LAK£  CO. 

o. 


SCALE  /''ZOO' 


*£  S, 


ff3/p29c/r 


Co.  Sur 


FIG.  406. — A  farm  plat. 


Plats  of  Subdivisions. 

The  plats  of  subdivisions  and  allotments  in  cities  are  filed  with 
the  county  recorder  for  record,  and  must  be  very  complete  in 
their  information  concerning  the  location  and  size  of  the  various 


232 


ENGINEERING  DRAWING 


lots  and  parcels  composing  the  subdivisions,  Fig.  407.  All 
monuments  set  should  be  shown  and  all  measurements  of  lines 
and  angles  given,  so  that  it  will  be  possible  to  locate  any  lot  with 
precision. 

Sometimes  landowners  desire  to  use  these  maps  in  display  to 
prospective  buyers,  and  some  degree  of  embellishment  is  allowable, 


c 

Sffi 

TwT? 

60 

35 

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S3 

r 

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« 

3E^20 

V 

86 

85 

84 

83 

<?.? 

tfA 

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73 

78 

77 

76 

7S 

7<fs 

h 

7? 

7/ 

7<i7 

5^ 

5<? 

4 

«| 

/Jftj      \ 

40 

. 

,. 

- 

.. 

40 

40 

•• 

•• 

•10 

^ 

«£ 

•M'J()      \ 

'  SUBDI  V/5rION 

—  ^      3 "**  CF    TH£ 

^-&Ffi£&-^  r-£R  DOTy  ESTATE 

'  COLUMBUS.   O. 


FIG.  407. — A  city  subdivision. 


but  care  must  be  taken  not  to  overdo  the  ornamentation.  These 
drawings  are  usually  finished  as  blue  prints.  Fig.  408  is  an 
example  showing  an  acceptable  style  of  execution  and  finish. 

When  required  for  reproduction  to  small  size  for  illustrative 
purposes  a  rendering  such  as  shown  in  Fig.  409  is  sometimes 
effective. 


MAP  AND  TOPOGRAPHICAL  DRAWING 


233 


FIG.  408. — A  real  estate  display  map. 


-  MM 

-I  =!  J  J  J  J  J 


J  J  _l  _J  J  5 •]  -J  -I  _l  -J   _J 

JJJJJ=!s^J-iZSJS_l 


J  J  ±  r!  J  _J  =!  =r:  =!  zd  =J 
J  d  d 

J  _JJ  S^l  =i  =; 


FIG.  409. — A  shade  line  map. 


234 


ENGINEERING  DRAWING 


City  Plats. 

Under  this  head  is  included  chiefly  maps  or  plats  drawn  from 
subdivision  plats  or  other  sources  for  the  record  of  city  improve- 
ments These  plats  are  used  for  the  record  of  a  variety  of  infor- 
mation, such  as,  for  example,  the  location  of  sewers,water  mains, 
street  railways,  and  street  improvements.  One  valuable  use  is 


rr 


FIG.  410.  —  A  sewer  map. 


in  the  levying  of  assessments  for  street  paving,  sewers,  etc.  As 
they  are  made  for  a  definite  purpose  they  should  not  contain 
unnecessary  information,  and  hence  will  not  include  all  the 
details  as  to  sizes  of  lots,  location  of  monuments,  etc.,  which  are 
given  on  subdivision  plats. 

They  are  usually  made  on  mounted  paper  and  should  be  to  a 


MAP  AND  TOPOGRAPHICAL  DRAWING  235 

scale  large  enough  to  show  clearly  the  features  required,  100' 
and  200'  to  the  inch  are  frequent  scales,  and  as  large  as  50'  is 
sometimes  used.  For  smaller  cities  the  entire  area  may  be 
covered  by  one  map;  in  larger  cities  the  maps  are  made  in  con- 
venient sections  so  as  to  be  filed  readily. 

A  study  of  Fig.  410,  a  sewer  map,  will  show  the  general  treat- 
ment of  such  plats.  The  appearance  of  the  drawing  is  improved 
by  adding  shade  lines  on  the  lower  and  right  hand  side  of  the 
blocks,  i.e.,  treating  the  streets  and  water  features  as  depressions. 

A  few  of  the  more  important  public  buildings  are  shown,  to 
facilitate  reading.  The  various  wards,  subdivisions  or  districts 
may  be  shown  by  large  outline  letters  or  numerals  as  illustrated 
in  the  figure. 

Topographical  Drawing. 

As  before  defined,  a  complete  topographical  map  would  contain: 

(1)  The  imaginary  lines  indicating  the  divisions  of  authority 
or  ownership. 

(2)  The  geographical  position  of  both  the  natural  features  and 
the  works  of  man.     They  may  also  include  information  in  regard 
to  the  vegetation. 


FIG.  411. 

(3)  The  relief,  or  indication  of  the  relative  elevations  and 
depressions. 

The  relief,  which  is  the  third  dimension,  is  represented  in 
general  either  by  contours  or  by  hill  shading. 

A  contour  is  a  line  on  the  surface  of  the  ground  which  at  every 
point  passes  through  the  same  elevation,  thus  the  shore  line  of  a 
body  of  water  represents  a  contour.  If  the  water  should  rise 
one  foot  the  new  shore  line  would  be  another  contour,  with  one 
foot  "contour  interval."  A  series  of  contours  may  thus  be 
illustrated  approximately  by  Fig.  411. 


236 


ENGINEERING  DRAWING 


Fig.  412  is  a  perspective  view  of  a  tract  of  land.  Fig.  413  is  a 
contour  map  of  this  area,  and  Fig.  414  is  the  same  surface  shown 
with  hill  shading  by  hachures.  Contours  are  drawn  as  fine,  full 
lines,  with  every  fifth  one  of  heavier  weight,  and  the  elevations  in 


FIG.  412. 


feet  marked  on  them  at  intervals,  usually  with  the  sea  level  as 
datum.  They  may  be  drawn  with  a  swivel  pen,  Fig.  26,  or  with 
a  fine  pen  such  as  Gillott's  303.  On  paper  drawings  they  are 
usually  made  in  brown. 


FIG.  413. 


The  showing  of  relief  by  means  of  hill  shading  gives  a  pleasing 
effect  but  is  very  difficult  of  execution,  does  not  give  exact  eleva- 
tions and  would  not  be  applied  on  maps  to  be  used  for  engineering 
purposes.  They  may  sometimes  be  used  to  advantage  in  re- 


MAP  AND  TOPOGRAPHICAL  DRAWING 


237 


connoissance  maps,  or  in  small  scale  maps  for  illustration. 
There  are  several  systems,  of  which  hachuring  is  the  commonest. 
Fig.  415  illustrates  the  method  of  execution.  The  contours  are 
sketched  lightly  in  pencil  and  the  hachures  drawn  perpendicular 


FIG.  414. 


to  them,  starting  at  the  summit  and  making  heavier  strokes  for 
steeper  slopes.  The  rows  of  strokes  should  touch  the  pencil  line, 
to  avoid  white  streaks  along  the  contours. 

Fig.  416  is  a  topographic  map  of  the  site  of  a  proposed  filtra- 


FIG.  415. 


tion  plant,  and  illustrates  the  use  of  the  contour  map  as  the 
necessary  preliminary  drawing  in  engineering  projects.  Often 
on  the  same  drawing  there  is  shown,  by  lines  of  different  character, 
both  the  existing  contours  and  the  required  finished  grades. 


238 


ENGINEERING  DRAWING 


Water  Lining. 

On  topographic  maps  made  for  display  or  reproduction  the 
water  features  are  usually  finished  by  water-lining,"  running  a 
system  of  fine  lines  parallel  to  the  shore  lines,  either  in  black  or 
in  blue  (it  must  be  remembered  that  blue  will  not  photograph 
for  reproduction  nor  print  from  a  tracing).  Poor  water-lining 
will  ruin  the  appearance  of  an  otherwise  well  executed  map,  and  it 


Je/fersor?  Zo//ir?gers  fairs 


Saraft  J  Potre/f 


C/ara3  Me  Comb 


FIG.  416. — Contour  map  for  engineering  project. 

is  better  to  omit  it  rather  than  do  it  hastily  or  carelessly.  The 
shore  line  is  drawn  first,  and  the  water-lining  done  with  a  fine 
mapping  pen,  as  Gillott's  170  or  290,  always  drawing  toward  the 
body  and  having  the  preceding  line  to  the  left.  The  first  line 
should  follow  the  shore  line  very  closely,  and  the  distances  between 
the  succeeding  lines  gradually  increased  and  the  irregularities 
lessened.  Sometimes  the  weight  of  lines  is  graded  as  well  as  the 
intervals  but  this  is  a  very  difficult  operation  and  is  not  necessary 
for  the  effect. 


MAP  AND  TOPOGRAPHICAL  DRAWING  239 

A  common  mistake  is  to  make  the  lines  excessively  wavy^or 
rippled. 

In  water-lining  a  stream  of  varying  width,  the  lines  are  not  to 
be  crowded  so  as  to  be  carried  through  the  narrow  portions,  but 
corresponding  lines  should  be  brought  together  in  the  middle  of 
the  stream  as  illustrated  in  Fig.  417.  Care  should  be  taken  to 
avoid  any  spots  of  sudden  increase  or  decrease  in  spacing. 


FIG.  417. — Water  lining. 

Topographic  Symbols. 

The  various  symbols  used  in  topographic  drawing  may  be 
grouped  under  four  heads : 

(1)  Culture,  or  the  works  of  man. 

(2)  Relief — relative  elevations  and  depressions. 

(3)  Water  features. 

(4)  Vegetation. 

When  color  is  used  the  culture  is  done  in  black,  the  relief  in 
brown,  the  water  features  in  blue,  and  the  vegetation  in  black 
or  green. 

These  symbols,  used  to  represent  characteristics  on  the  earth's 
surface,  are  made  when  possible  to  resemble  somewhat  the 
features  or  object  represented  as  it  would  appear  either  in  plan 
or  elevation.  We  cannot  attempt  to  give  symbols  for  all  the 
features  that  might  occur  in  a  map,  indeed  one  may  have  to 
invent  symbols  for  some  particular  locality. 

Fig.  418  illustrates  a  few  of  the  conventional  symbols  used  for 
cultures  or  the  works  of  man,  and  no  suggestion  is  needed  as  to 
the  method  of  their  execution.  When  the  scale  used  is  large, 
houses,  bridges,  roads  and  even  tree  trunks  can  be  plotted  so 


240 


ENGINEERING  DRAWING 


E/ectric  Railway 

-7/^£v7f#~)^.  ~*Tvnn~ei*~ 

City  ortt/lage 


Bridge 


, Jill 

nfifflr 

Fet 

^'  1 
I 


Privafe  ffoads 


Ferry 


Sing/e  Track 


Dot/b/e  Track 
ffai/roads 


Foraf 


Dam 


State  Line 

County  Line 

Township  L/ne 

C/ry  or 


T      T     T      T      T 
Te/egrap/?  or 
Te/epnor/e 


Hedge 

AA/WNA/VW 
ffai/  or  Worm  fence 


'w 

•«••••*„„, 

Levees  ' 

x  B.M.        ^ 
Bench  Mark  M/fJeor 
&  Quarry 

Triangu/ofiorr    B 
5 fa f /'on 


SfoneSence 
W/re  Fence 


frvflerfy  iris  nof/ittced 


t 

Church 

F»  mL.S.5. 

•      .     Life-sav/na 
Sc/?ot?/       Station 


FIG.  418.— Culture. 


Location,  n'a  or t/r/////??  we//.. .O 

O//  We//. • 

Smaf/  O/'/  We//. • 

Dry  Ho/e.... -cj>- • 

Symtio/  of  abandonment. .  V,  thus,  ...)& 

A/umber  of  we//s,  thus, £>/g 

Show  vo/vmes,  thus -££- 


£ryr/o/e  M//?  shomagrefo//. 
Gas 


*; 


-?- 


FIG.  419. — Oil  and  gas  symbols. 


Determined 
E/evafion 


Sand 


Mud  flat 


FIG.  420.— Relief. 


MAP  AND  TOPOGRAPHICAL  DRAWING 


241 


that  their  principal  dimensions  can  be  scaled.  A  small  scale 
map  can  give  by  its  symbols  only  the  relative  locations. 

Fig.  419  gives  the  standard  symbols  used  in  the  development 
of  oil  and  gas  fields. 

Fig.  420  contains  symbols  used  to  show  relief. 

Water  features  are  illustrated  in  Fig.  421. 

In  Fig.  422  is  shown  some  of  the  commoner  symbols  for  vege- 
tation and  cultivation. 

Draftsmen  should  keep  in  mind  the  purpose  of  the  map,  and 
the  relative  importance  of  features  should  be  in  some  measure 
indicated  by  their  prominence  or  strength,  gained  principally 


Lock 


Jrjfermiftenf  Streams 


Dry  Lake 


Submarine  Cortfot/rs 


Fresh  Marsh  Sa/t  Marsh         Submerged  Marsh          T/ata/ F/at 


FIG.  421.— Water  features. 


by  the  amount  of  ink  used.  For  instance,  in  a  map  made  for 
military  maneuvering  a  cornfield  might  be  an  important  feature, 
or  in  maps  made  to  show  the  location  of  special  features,  such  as 
fire  hydrants,  etc.,  these  objects  would  be  indicated  very  plainly. 
This  principle  calls  for  some  originality  to  meet  varying  cases. 

A  common  fault  of  the  beginner  is  to  make  symbols  too  large. 
The  symbols  for  grass,  shown  under  "meadow,"  Fig.  422,  if  not 
made  and  spaced  correctly  will  spoil  the  entire  map.  This 
symbol  is  composed  of  from  five  to  seven  short  strokes  radiating 
from  a  common  center  and  starting  along  a  horizontal  line,  as 


242 


ENGINEERING  DRAWING 


shown  in  the  enlarged  form,  each  tuft  beginning  and  ending 
with  a  mere  dot.  Always  place  the  tufts  with  the  bottom  parallel 
to  the  border  and  distribute  them  uniformly  over  the  space, 
but  not  in  rows.  A  few  incomplete  tufts,  or  rows  of  dots  improve 
the  appearance.  Grass  tufts  should  never  be  as  heavy  as  tree 
symbols. 

In  drawing  the  symbol  for  deciduous  trees  the  sequence  of 
strokes  shown  should  be  followed. 


Meadow 


t,  ft  r  *  t 

i   t  f  {  f  f 

Willows 


O  (5  Q  O  fj)  O 
'>  O  O  Q  O  0> 
O  O>  O  C>  C?  Q 


Orchard 


, 

*--^  «     >  *  &  c?o         frisS  *s<x  --ovi         ***V*  **-:< 

Evergreen  Trees 


Deciduous  Trees^ 


Oak  Trees 


Pine,  Willow&  Brush  Cleared  Land  Cultivated  Land 

tttuu  .  rr^vrrur    y^y^Vi 

.t,  ,i,  ^-  a,  ^,  .u    i    f  I  i  i  i  i  i 
*>i^  iiii 


Corn 


Tobacco 


Vineyard 


FIG.  422. — Vegetation. 

The  topographic  map,  Fig.  423,  is  given  to  illustrate  the  general 
execution  and  placing  of  symbols. 

Fig.  424  is  a  type  of  map  made  by  landscape  architects  in  the 
study  of  improvements  for  parks,  additions,  and  estates.  Shadows 
are  often  employed  on  these  maps  to  show  the  comparative 
heights  of  tall  trees,  low  trees,  and  shrubs. 
Lettering. 

The  style  of  lettering  on  a  topographic  map  will  of  course 
depend  upon  the  purpose  for  which  the  map  is  made.  If  for 
construction  purposes,  such  as  a  contour  map  for  the  study  of 
municipal  problems,  street  grades,  plants,  or  railroads,  the  single- 
stroke  gothic  and  Reinhardt  is  to  be  preferred.  For  a  finished 
map  vertical  Roman  letters  for  land  features,  and  inclined 


MAP  AND  TOPOGRAPHICAL  DRAWING 


243 


244 


ENGINEERING  DRAWING 


MAP  AND  TOPOGRAPHICAL  DRAWING  245 

Roman  and  stump  letters  for  water  features  should  be  used. 
The  scale  should  always  be  drawn  as  well  as  stated. 

The  well  known  maps  of  the  Coast  Survey  and  Geological 
•Survey  are  good  examples  of  this  kind  of  map.  The  quadrangle 
sheets  issued  by  the  topographic  branch  of  the  U.  S.  Geological 
Survey  are  excellent  examples  and  so  easily  available  that  every 
draftsman  should  be  familiar  with  them.  These  sheets  represent 
15  min.  of  latitude  and  15  min.  of  longitude,  and  the  entire 
United  States  is  being  mapped  by  the  department.  In  1911  about 
81  per  cent,  of  New  York  state,  50%  of  Pennsylvania,  and  67% 
of  Ohio,  and  other  states  in  somewhat  the  same  percentages 
are  already  completed.  These  maps  may  be  secured  for  5 
cents  each  (not  stamps)  by  addressing  The  Director,  U.  S.  Geo- 
logical Survey,  Washington,  D.  C.,  from  whom  information  as  to 
the  completion  of  any  particular  locality  or  the  progress  in  any 
state  may  be  had.  The  scale  of  these  maps  is  approximately 
1  inch  to  the  mile.  Some  territory  in  the  West  has  been  mapped 
to  1/2  inch  to  the  mile.  On  the  back  of  each  sheet  will  be 
found  a  code  of  the  conventional  symbols  used  by  the  depart- 
ment. 
Profiles. 

Perhaps  no  kind  of  drawing  is  used  more  by  civil  engineers  than 
the  ordinary  profile,  which  is  simply  a  vertical  section  taken 
along  a  given  line  either  straight  or  curved.  Such  drawings  are 
indispensable  in  problems  of  railroad  construction,  highway  and 
street  improvements,  sewer  construction,  and  many  other  prob- 
lems where  a  study  of  the  surface  of  the  ground  is  required. 
Very  frequently  engineers  other  than  civil  engineers  are  called 
upon  to  make  these  drawings.  Several  different  types  of  pro- 
file and  cross-section  paper  are  in  use  and  may  be  found  in  the 
catalogues  of  the  various  firms  dealing  in  drawing  materials. 
One  type  of  profile  paper  in  common  use  is  known  as  " Plate  A" 
in  which  there  are  four  divisions  to  the  inch  horizontally  and 
twenty  to  the  inch  vertically.  Other  divisions  which  are  used 
are  4  X  30  to  the  inch  and  5  X  25  to  the  inch.  At  intervals 
both  horizontally  and  vertically  somewhat  heavier  lines  are 
made  in  order  to  facilitate  reading. 

Horizontal  distances  are  plotted  as  abscisses  and  elevations  as 
ordinates.     The  vertical  distances  representing  elevations,  be- 
ing plotted  to  larger  scale,  a  vertical  exaggeration  is  obtained 
16 


246 


ENGINEERING  DRAWING 


which  is  very  useful  in  studying  the  profile  for  the  establishing 
of  grades.  The  vertical  exaggeration  is  sometimes  confusing  to 
the  layman  or  inexperienced  engineer,  but  ordinarily  a  profile 
will  fail  in  the  purpose  for  which  it  was  intended  if  the  horizontal 
and  vertical  scale  are  the  same.  Again  the  profile  unless  so 

H/gbest  /b/rtf  of  Excavation 
6o/d M// £/.  £34.0  /     \ 


Proposed  Bottom  ofCario/  £/.  +40° 

Mean  Sta  JLere/  Q 


33  34  35  36  37  38 

Miles 
FIG.  425.— Profile.     (Vert,  scale  50  times  hor.) 

distorted  would  be  a  very  long  and  unwieldy  affair,  if  not  entirely 
impossible  to  make.  The  difference  between  profiles  with  and 
without  vertical  exaggeration  is  shown  in  Figs.  425  and  426. 
Fig.  427  is  a  profile  together  with  the  alignment  which  is  drawn 


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Miles 
FIG.  426.— Profile.     (Vert,  and  hor.  scales  equal.) 

just  below  the  profile  proper.  This  figure  represents  a  common 
method  employed  by  draftsmen  in  railroad  offices.  Attention 
is  called  to  the  method  of  straightening  out  the  alignment. 
Such  a  method  is  also  used  on  surveys  for  improvement  of  high- 
ways and  the  like. 


MAP  AND  TOPOGRAPHICAL  DRAWING 


247 


CHAPTER  XIII. 
DUPLICATION  AND  DRAWING  FOR  REPRODUCTION. 

As  has  been  stated,  working  drawings  or  any  drawings  which 
are  to  be  duplicated  are  traced.  Sometimes  drawings  of  a  tem- 
porary character  are,  for  economy,  traced  on  white  tracing 
paper,  but  tracing  cloth  is  more  transparent,  much  more  durable, 
prints  better,  and  is  easier  to  work  on. 

Drawings  intended  for  blue  printing  are  sometimes  penciled 
and  inked  on  bond  or  ledger  paper.  A  print  from  these  papers 
requires  more  exposure  and  has  a  mottled  appearance,  showing 
plainly  the  texture  and  watermarks. 

Tracing  cloth  is  a  fine  thread  fabric,  sized  and  transparentized 
with  a  starch  preparation.  The  three  brands  Excelsior,  Imperial, 
and  Kohinoor  are  recommended.  The  smooth  side  is  considered 
by  the  makers  as  the  right  side,  but  most  draftsmen  prefer  to 
work  on  the  dull  side,  principally  because  it  will  take  a  pencil 
mark.  The  cloth  should  be  tacked  down  smoothly  over  the 
pencil  drawing  and  its  selvage  torn  off.  It  should  then  be  dusted 
with  chalk  or  prepared  pounce  and  rubbed  off  with  a  cloth,  to 
remove  traces  of  grease  which  sometimes  prevents  the  flow  of 
ink  (a  blackboard  eraser  serves  very  well  for  this  purpose) . 

To  insure  good  printing  the  ink  should  be  perfectly  black, 
and  the  outline  should  be  made  with  a  bolder  line  than  would 
be  used  on  paper,  as  the  contrast  of  a  white  line  on  the  blue 
ground  is  not  so  strong  as  the  black  line  on  a  white  ground. 
Red  ink  should  not  be  used  unless  it  is  desired  to  have  some  lines 
very  inconspicuous.  Blue  ink  will  not  print.  Sometimes,  in 
maps,  diagrams,  etc.,  to  avoid  confusion  of  lines,  it  is  desired  to 
use  colored  inks  on  the  tracing;  if  so  a  little  Chinese  white  added 
will  render  them  opaque  enough  to  print. 

Sometimes,  instead  of  section  lining,  sections  are  indicated  by 
rubbing  a  pencil  tint  over  the  surface  on  the  dull  side,  or  by 
putting  a  wash  of  color  on  the  tracing  either  on  the  smooth  side 
or  on  the  dull  side.  These  tints  will  print  in  lighter  Hue  than 
the  background. 

248 


DUPLICATION   AND   DRAWING   FOR   REPRODUCTION    249 

Ink  lines  may  be  removed  from  tracing  cloth  by  rubbing  with 
a  pencil  eraser.  A  triangle  should  be  slipped  under  the  tracing 
to  give  a  harder  surface.  The  rubbed  surface  should  afterward 
be  burnished  with  an  ivory  or  bone  burnisher,  or  with  a  piece  of 
talc  (tailor's  chalk)  or,  in  the  absence  of  other  means,  with  the 
thumb  nail.  In  tracing  a  part  that  has  been  section  lined,  a 
piece  of  white  paper  should  be  slipped  under  the  cloth  and  the 
section  lining  done  without  reference  to  the  drawing  underneath. 

For  an  unimportant  piece  of  work  it  is  possible  to  make  a 
freehand  tracing  from  an  accurate  pencil  drawing  in  perhaps 
one-half  the  time  required  for  a  mechanical  drawing. 

Tracing  cloth  is  very  sensitive  to  atmospheric  changes,  often 
expanding  over  night  so  as  to  require  restretching.  If  the  com- 
plete tracing  cannot  be  finished  during  the  day  some  views 
should  be  finished,  and  no  figure  left  with  only  part  of  its  lines 
traced. 

Water  will  ruin  a  tracing,  and  moist  hands  or  arms  should  not 
come  in  contact  with  the  cloth.  The  habit  should  be  formed  of 
keeping  the  hands  off  drawings.  It  is  a  good  plan,  in  both  drawing 
and  tracing  on  large  sheets,  to  cut  a  mask  of  drawing  paper  to 
cover  all  but  the  view  being  worked  on.  Unfinished  drawings 
should  always  be  covered  over  night. 

Tracings  may  be  cleaned  of  pencil  marks  and  dirt  by  rubbing 
over  with  a  rag  or  waste  dipped  in  benzine  or  gasolene. 

The  starch  may  be  washed  from  scrap  tracing  cloth  to  make 
penwipers  or  cloths. 

The  tracing  is  a  "  master  drawing"  and  should  never  be  allowed 
to  .be  taken  out  of  the  office,  but  prints  may  be  made  from  it  by 
one  of  the  processes  described  below.  Any  number  of  prints 
may  be  taken  from  one  tracing. 

Blue  Printing. 

The  simplest  of  the  printing  processes  is  blue  printing,  made  by 
exposing  a  piece  of  sensitized  paper  in  contact  with  the  tracing  to 
sunlight  or  electric  light  in  a  printing  frame  made  for  the  purpose. 
The  blue  print  paper  is  a  white  paper  free  from  sulphites,  coated 
with  a  solution  of  citrate  of  iron  and  ammonia,  and  ferricyanide  of 
potassium.  On  exposure  to  the  light  a  chemical  action  takes 
place,  which  when  fixed  by  washing  in  water  gives  a  strong  blue 
color.  The  parts  protected  from  the  light  by  the  black  lines 


250  ENGINEERING  DRAWING 

of  the  tracing  wash  out,  leaving  the  white  paper.  Blue-print 
paper  is  usually  bought  ready  sensitized,  and  may  be  had  in  dif- 
ferent weights  and  different  degrees  of  rapidity.  When  fresh  it 
is  of  a  yellowish  green  color,  and  an  unexposed  piece  should  wash, 
out  perfectly  white.  With  age  or  exposure  to  light  or  air,  it 
turns  to  a  darker  gray-blue  color,  and  spoils  altogether  in  a 
comparatively  short  time.  In  some  emergency,  it  may  be  neces- 
sary to  prepare  blue-print  paper.  The  following  formula  will 
give  a  paper  requiring  about  three  minutes'  exposure  in  bright 
sun-light. 

(1)  Citrate  of  iron  and  ammonia  (brown  scales)  2  oz.,  water 
8  oz. 

(2)  Red  prussiate  of  potash  11/2  oz.,  water  8  oz. 
Keep  in  separate  bottles  away  from  the  light. 

To  prepare  paper  take  equal  parts  of  (1)  and  (2)  and  apply 
evenly  to  the  paper  with  a  sponge  or  camel's-hair  brush,  by 
subdued  light. 

To  make  a  blue  print. 

Lay  the  tracing  in  the  frame  with  the  inked  side  toward  the 
glass,  and  place  the  paper  on  it  with  its  sensitized  surface  against 
the  tracing.  Lock  up  in  the  frame  so  there  is  a  perfect  contact 


FIG.  428.— A  blue  print  frame. 

between  paper  and  cloth.  See  that  no  corners  are  turned  under. 
Expose  to  the  sunlight  or  electric  light.  If  a  frame  having  a 
hinged  back  is  used,  Fig.  428,  one  side  may  be  opened  for  ex- 
amination. When  the  paper  is  taken  from  the  frame  it  will  be  a 
bluish  gray  color  with  the  heavier  lines  lighter  than  the  back- 
ground, the  lighter  lines  perhaps  not  being  distinguishable.  Put 


DUPLICATION  AND   DRAWING  FOR   REPRODUCTION    251 

the  print  for  about  five  minutes  in  a  bath  of  running  water, 
taking  care  that  air  bubbles  do  not  collect  on  the  surface,  and 
hang  up  to  dry.  An  overexposed  print  may  often  be  saved  by 
prolonged  washing.  The  blue  color  may  be  intensified  and  the 
whites  cleared  by  dipping  the  print  for  a  moment  into  a  bath 
containing  a  solution  of  potassium  bichromate  (1  to  2  oz.  of 
crystals  to  a  gallon  of  water),  and  rinsing  thoroughly.  This 
treatment  will  bring  back  a  hopelessly  *'  burned  "  print. 

To  be  independent  of  the  weather,  most  concerns  use  electric 
printing  machines,  either  cylindrical,  in  which  a  lamp  is  lowered 
automatically  inside  a  glass  cylinder  about  which  the  tracing  and 
paper  are  held,  or  continuous,  in  which  the  tracing  and  paper 
are  fed  through  rolls,  and  in  some  machines,  printed,  washed 
and  dried  in  one  operation. 

Prints  too  large  for  a  frame  may  be  made  in  sections  and 
pasted  together. 

In  an  emergency  it  is  possible  to  make  a  fair  print  by  holding 
tracing  and  paper  to  the  sunlight  against  a  window  pane. 

A  clear  blue  print  may  be  made  from  a  typewritten  sheet 
which  has  been  written  with  a  sheet  of  carbon  paper  back  of  it, 
so  that  it  is  printed  on  both  sides. 

Van  Dyke  paper  is  a  thin  sensitized  paper  which  turns  dark 
brown  on  exposure  and  fixing,  which  is  done  by  first  washing  in 
water,  then  in  a  bath  of  hyposulphite  of  soda,  and  washing 
again  thoroughly.  A  reversed  negative  of  a  tracing  may  be 
made  on  it  by  exposing  with  the  inked  side  of  the  tracing  next 
to  the  sensitized  side  of  the  paper.  This  negative,  if  printed  on 
blue-print  paper  will  give  a  blue-line  print  with  white  back- 
ground. 

The  Van  Dyke  negative  may  be  "  transparentized  "  so  as  to 
print  in  one-half  to  one-third  the  time,  by  a  solution  sold  by  the 
dealers,  or  by  a  solution  of  paraffin  cut  in  benzine. 

A  direct  black  paper  is  made  by  the  Carlton  Supply  Co., 
Brooklyn,  N.  Y.,  which  is  printed  and  washed  the  same  as  a 
blue  print  and  gives  permanent  black  lines  on  white  ground. 

White  ground  prints  have  the  advantage  that  additions  or 
notes  may  be  made  in  ink  or  pencil,  and  that  tints  may  be  added. 

Changes  are  made  on  blue  prints  by  writing  or  drawing  with 
any  alkaline  solution,  such  as  of  soda  or  potash,  which  bleaches 
the  blue.  A  little  gum  arable  will  prevent  spreading.  A  tint 


252  ENGINEERING  DRAWING 

may  be  given  by  adding  a  few  drops  of  red  or  other  colored  ink 
to  the  solution.-  Chinese  white  is  sometimes  used  for  white- 
line  changes  on  a  blue  print. 

A  blue  print  may  be  made  from  a  drawing  made  in  pencil  or 
ink  on  bond  paper  or  tracing  paper,  but  with  thick  drawing 
paper  the  light  will  get  under  the  lines  and  destroy  the  sharpness. 
A  print  may  be  made  from  Bristol  or  other  heavy  white  paper 
by  turning  it  with  the  ink  side  against  the  paper,  thereby  revers- 
ing the  print,  or  by  making  a  Van  Dyke  negative,  with  a  long 
exposure;  or  it  may  be  soaked  in  benzine  and  printed  while  wet. 
The  benzine  will  evaporate  and  leave  no  trace. 

A  blue-line  print  may  be  taken  from  a  blue  print  by  fading  the 
blue  of  the  first  print  in  weak  ammonia  water,  washing  thor- 
oughly, then  turning  it  red  in  a  weak  solution  of  tannic  acid, 
and  washing  again.  Transparentizing  at  this  stage  will  assist. 

In  printing  a  number  of  small  tracings  they  may  be  fastened 
together  at  their  edges  with  gummed  stickers  and  handled  as  a 
single  sheet. 

Any  white  paper  may  be  rendered  sufficiently  translucent  to 
give  a  good  blue  print,  with  the  " transparentizing  solutions" 
mentioned  before,  and  a  machine  called  the  "  mechanigraph " 
is  now  on  the  market  which  does  this  commercially,  enabling 
drawings  to  be  made  on  white  paper  in  pencil,  from  which 
finished  prints  can  be  made  without  inking  or  tracing. 

The  methods  of  the  hectograph  or  gelatine  pad,  neostyle, 
mimeograph,  etc.,  often  used  for  duplicating  small  drawings,  are 
too  well  known  to  need  description  here. 

Large  drawings  or  drawings  in  sets  are  often  photographed  to 
reduced  size  and  blue  prints  or  other  prints  made  from  the 
negatives  giving  convenient  prints  for  reference. 
Drawing  for  Reproduction. 

By  this  term  is  meant  the  preparation  of  drawings  for  repro- 
duction by  one  of  the  photo-mechanical  processes  used  for 
making  plates,  or  "cuts,"  as  they  are  often  called,  for  printing 
purposes.  Such  drawings  will  be  required  in  the  preparation 
of  illustrations  for  books  and  periodicals,  for  catalogues  or  other 
advertising,  and  incidentally  for  patent  office  drawings,  which 
are  reproduced  by  photo-lithography. 

Line  drawings  are  usually  reproduced  by  the  process  known  as 
zinc  etching,  in  which  the  drawing  is  photographed  on  a  process 


DUPLICATION  AND    DRAWING   FOR   REPRODUCTION    253 

plate,  generally  with  some  reduction,  the  negative  film  reversed 
and  printed  so  as  to  give  a  positive  on  a  sensitized  zinc  plate 
(when  a  particularly  fine  result  is  desired,  a  copper  plate  is  used) 


zMMvmmmz^ 


FIG.  429. — Drawing  for  one-half  reduction. 


FIG.  430. 


which  is  etched  with  acid,  leaving  the  lines  in  relief  and  giving, 
when  mounted  type-high  on  a  wood  base,  a  block  which  can 
be  printed  along  with  type  in  an  ordinary  printing  press. 


254 


ENGINEERING  DRAWING 


Drawings  for  zinc  etching  should  be  made  on  smooth  white 
paper  or  tracing  cloth  in  black  drawing  ink  and  preferably 
larger  than  the  required  reproduction. 

If  it  is  desired  to  preserve  the  hand-drawTn  character  of  the 


FIG.  431. — Drawing  for  "two- thirds"  reduction. 

original,  the  reduction  should  be  slight;  but  if  a  very  smooth 
effect  is  wanted,  the  drawing  may  be  as  much  as  3  or  4  times  as 
large  as  the  cut.  The  best  general  size  is  one  and  one-half 
times  linear.  Fig.  429  illustrates  the  appearance  of  an  original 


FIG.  432. 

drawing  and  Fig.  430  the  same  drawing  reduced  one-half.  Fig. 
431  is  another  original  which  has  been  reduced  two-thirds,  Fig. 
432.  The  coarse  appearance  of  these  originals  and  the  open 
shading  should  be  noticed. 

A  reducing  glass,  a  concave  lens  mounted  like  a  reading  glass 


DUPLICATION   AND   DRAWING  FOR   REPRODUCTION    255 

is  sometimes  used  to  aid  in  judging  the  appearance  of  a  drawing 
on  reduction.  If  lines  are  drawn  too  close  together  the  space 
between  them  will  choke  in  the  reproduction  and  mar  the  effect. 

One  very  convenient  thing  not  permissible  in  other  work  may 
be  done  on  drawings  for  reproduction — any  irregularities  may 
be  corrected  by  simply  painting  out  with  Chinese  white.  If  it  is 
desired  to  shift  a  figure  after  it  has  been  inked  it  may  be  cut  out 
and  pasted  on  in  the  required  position.  The  edges  thus  left 
will  not  trouble  the  engraver,  as  they  will  be  tooled  out  when 
the  etching  is  finished. 

Wash  drawings  and  photographs  are  reproduced  in  a  similar 
wTay  on  copper  by  what  is  known  as  the  half-tone  process  in 
which  the  negative  is  made  through  a  ruled  " screen"  in  front  of 
the  plate,  which  breaks  up  the  tints  into  a  series  of  dots  of  varying 
size.  Screens  of  different  fineness  are  used  for  different  kinds  of 
paper,  from  the  coarse  screen  newspaper  half-tone  of  80  to  100 
lines  to  the  inch,  the  ordinary  commercial  and  magazine  half- 
tone of  133  lines,  to  the  fine  150  and  175  line  half-tones  for  print- 
ing on  very  smooth  coated  paper. 

Photographic  prints  for  reproduction  are  often  retouched  and 
worked  over,  shadows  being  strengthened  with  water  color, 
high-lights  accented  with  Chinese  white,  and  details  brought 
out  that  would  otherwise  be  lost.  In  catalogue  illustration  of 
machinery,  etc.,  objectionable  backgrounds  or  other  features  can 
be  removed  entirely.  Commercial  retouchers  use  the  air-brush 
as  an  aid  in  this  kind  of  work,  spraying  on  color  with  it  very 
rapidly  and  smoothly  and  securing  results  not  possible  in  hand- 
work. 

Half  tones  cost  from  ten  to  fifteen  cents  per  sq.  in.  with  a 
minimum  price  of  $1.00,  and  zinc  etching  from  five  to  seven 
cents  per  sq.  in.  with  a  minimum  of  sixty  cents. 

Line  illustrations  are  sometimes  made  by  the  "wax  process" 
in  which  a  blackened  copper  plate  is  covered  with  a  very  thin 
film  of  wax,  on  which  a  drawing  may  be  photographed  and  its 
outline  scratched  through  the  wax  by  hand  with  different  sized 
gravers.  The  lettering  is  set  up  in  type  and  pressed  into  the 
wax;  more  wax  is  then  piled  up  in  the  wider  spaces  between  the 
lines  and  an  electrotype  taken.  Drawings  for  this  process  need 
not  be  specially  prepared,  as  the  work  may  be  done  even  from  a 
pencil  sketch  or  blue  print.  Wax  plates  print  very  clean  and 


256 


ENGINEERING  DRAWING 


sharp  and  the  type-lettering  gives  them  a  finished  appearance, 
but  they  lack  the  character  of  a  drawing,  are  more  expensive  than 
zinc  etching  and  often  show  mistakes  due  to  the  lack  of  famili- 
arity of  the  engraver  with  the  subject.  Fig.  433  shows  the 
characteristic  appearance  of  a  wax  plate. 


Gear  Bracket  Bearing,  1  O.I. 


FIG.  433.— A  wax  plate. 


Maps  and  large  drawings  are  usually  reproduced  by  lithog- 
raphy, in  which  the  drawing  is  either  photographed  or  engraved 
on  a  lithographic  stone,  and  transferred  from  this  either  to  another 
stone  from  which  it  is  printed  or  in  the  offset  process  to  a  thin 
sheet  of  zinc  which  is  wrapped  around  a  cylinder,  and  prints  to 
a  rubber  blanket  which  in  turn  prints  on  the  paper. 


CHAPTER  XIV. 


NOTES  ON  COMMERCIAL  PRACTICE. 

Under  this  heading  there  is  included  a  number  of  suggestions 
and  items  of  miscellaneous  information  for  student  and  drafts- 
man. 

To  Sharpen  a  Pen. 

Pens  that  are  in  constant  use  require  frequent  sharpening 
and  every  draftsman  should  be  able  to  keep  his  own  pens  in 
fine  condition.  The  points  of  a  ruling  pen  should  have  an  oval 
or  elliptical  shape  as  (a)  Fig.  434,  with  the  nibs  exactly  the  same 
length,  (b)  is  a  worn  pen  and  (c)  (d)  and  (e)  incorrect  shapes* 


B  C  D  £ 

FIG.  434. — Corrected  ruling  pen  points. 

sometimes  found.  The  best  stone  to  use  is  a  hard  Arkansas 
knife  piece  or  knife  edge.  It  is  best  to  soak  a  new  stone  in  oil 
for  several  days  before  using.  The  ordinary  carpenter's  oil 
stone  is  too  coarse  to  be  used  for  instruments. 

The  nibs  must  first  be  brought  to  the  correct  shape  as  (a)  and 
as  indicated  on  the  dotted  lines  of  (b),  (c)  and  (d).  This  is 
done  by  screwing  the  nibs  together  until  they  touch  and,  hold- 
ing the  pen  as  in  drawing  a  line,  drawing  it  back  and  forth  on  the 
stone,  starting  the  stroke  with  the  handle  at  perhaps  30  degrees 
with  the  stone,  and  swinging  it  up  past  the  perpendicular  as  the 

257 


258  ENGINEERING  DRAWING 

line  across  the  stone  progresses.  This  will  bring  the  nibs  to 
exactly  equal  shape  and  length,  leaving  them  very  dull.  They 
should  then  be  opened  slightly  and  each  blade  sharpened  in 
turn  until  the  bright  spot  on  the  end  has  just  disappeared, 
holding  the. pen  as  in  Fig.  435  at  a  small  angle  with  the  stone 
and  rubbing  it  back  and  forth  with  a  slight  oscillating  or  rocking 
motion  to  conform  to  the  shape  of  the  blade.  The  pen  should 
be  examined  frequently  and  the  operation  stopped  just  when  the 
reflecting  spot  has  vanished.  A  pocket  magnifying  glass  may 
be  of  aid  in  examining  the  points.  The  blades  should  not  be 
sharp  enough  to  cut  the  paper  when  tested  by  drawing  a  line, 
without  ink,  across  it.  If  over-sharpened  the  blades  should 


FIG.  435. 


again  be  brought  to  touch  and  a  line  drawn  very  lightly  across 
the  stone  as  in  the  first  operation.  When  tested  with  ink  the 
pen  should  be  capable  of  drawing  clean  sharp  lines  down  to  the 
finest  hair  line.  If  these  finest  lines  are  ragged  or  broken  the  pen 
is  not  perfectly  sharpened.  It  should  not  be  necessary  to  touch 
the  inside  of  the  blades  unless  a  bur  has  been  formed,  which 
might  occur  with  very  soft  metal  or  by  using  too  coarse  a  stone. 
In  such  cases  the  blades  should  be  opened  wide  and  the  bur 
removed  by  a  very  light  touch,  with  the  entire  inner  surface  of 
the  blade  in  contact  with  the  stone,  which  of  course  must  be 
sufficiently  thin  to  be  inserted  between  the  blades.  The  beginner 
had  best  practise  by  sharpening  several  old  pens  before  attempt- 
ing to  sharpen  a  good  instrument.  After  using,  the  stone  should 
be  wiped  clean  and  a  drop  of  oil  rubbed  over  it  to  prevent 
hardening  and  glazing. 

To  Make  a  Lettering  Pen.* 

Lettering  should  never  be  done  with  the  ruling  pen,  but  some 
draftsmen  make  a  lettering  pen  for  coarse  single-stroke  letters, 
*  Described  by  Prof.  C.  L.  Adams. 


NOTES  ON  COMMERCIAL  PRACTICE 


259 


out  of  an  old  ruling  pen  by  first  rubbing  the  point  very  blunt, 
then  grinding  the  blades  together  to  a  conical  shape,  and  finally 
shaping  a  ball  end  on  the  blunted  point.  This  pen  will  make  a 
line  somewhat  similar  to  that  made  by  the  Payzant  and  Shepard 
pens.  Its  handle  should  be  plainly  cut  or  marked  to  distinguish 
it  from  a  ruling  pen. 

Line  Shading. 

Line  shading,  the  rendering  of  the  effect  of  light  and  shade  by 
ruled  lines,  was  referred  to  in  Chapter  VI  as  "  an  accomplishment 
not  usual  among  ordinary  draftsmen."  The  reason  for  this  is 
that  it  is  not  used  at  all  on  working  drawings  and  the  drafts- 
man engaged  in  that  work  does  not  have  occasion  to  apply  it. 
It  is  used,  however,  on  display  drawings,  illustrations,  patent 
office  drawings,  and  the  like,  and  is  worthy  of  study  if  one  is 
interested  in  this  class  of  finished  work. 


FIG.  436. — Flat  and  graded  tints. 


To  execute  line  shading  rapidly  and  effectively  requires  con- 
tinued practice  and  some  artistic  ability,  and,  as  much  as  any- 
thing else,  good  judgment  in  knowing  when  to  stop.  Often  the 
simple  shading  of  a  shaft  or  other  round  member  will  add  greatly 
to  the  effectiveness  of  a  drawing,  and  may  even  save  making 
another  view,  or  a  few  lines  of  "  surface  shading  "  on  a  flat  surface 
will  show  its  position  and  character.  The  pen  must  be  in  per- 
fect condition,  with  its  screw  working  very  freely. 

Fig.  436  shows  three  preliminary  exercises  in  flat  and  graded 
tints  in  which  the  pitch  or  distance  from  center  to  center  of  lines 
is  equal.  In  wide  graded  tints  as  (b)  and  (c)  the  setting  of  the 
pen  is  not  changed  for  every  line,  but  several  .lines  are  drawn, 


260 


ENGINEERING  DRAWING 


then  the  pen  changed  slightly  and  several  more  drawn.  Fig. 
437  is  an  application,  illustrating  the  rule  that  an  inclined 
illuminated  surface  is  lightest  nearest  the  eye  and  an  inclined  sur- 
face in  shade  is  darkest  nearest  the  eye. 

With  the  light  coming  in  the  conventional  direction  a  cylinder 
would  be  illuminated  as  in  Fig.  438.     Theoretically  the  darkest 


^  Shade Snt 


FIG.  437. 


FIG.  438. 


line  'is  at  the  tangent  or  shade  line  and  the  lightest  part  at  the 
"brilliant  line"  where  the  light  is  reflected  directly  to  the  eye. 
Cylinders  shaded  according  to  this  theory  are  the  most  effective, 
but  often  in  practice  the  dark  side  is  carried  out  to  the  edge,  and 
in  small  cylinders  the  light  side  is  left  unshaded. 


ABC  D  3"   £ 

FIG.  439. — Cylinder  shading. 


Fig.  439  is  a  row  of  cylinders  of  different  sizes.  The  effect  of 
polish  is  given  by  leaving  several  brilliant  lines,  as  might  occur 
if  the  light  came  in  through  several  windows. 

A  conical  surface  may  be  shaded  by  driving  a  fine  needle  at 
the  apex  and  swinging  a  triangle  about  it,  as  in  (A)  Fig.  440. 


NOTES  ON  COMMERCIAL  PRACTICE 


261 


To  avoid  a  blot  at  the  apex  of  a  complete  cone  the  needle  may 
be  driven  on  the  extension  of  the  side  as  in  (B),  or  it  may  be 
shaded  by  parallel  lines  as  in  (C). 
Fig.  441  illustrates  several  applications  of  these  principles. 


A  B  C 

FIG.  440. — Cone  shading. 


FIG.  441. — Shaded  single  curved  surfaces. 


FIG.  442.— Spheres. 

It  is  in  the  attempt  to  represent  double  curved  surfaces  that 
the  line-shader  meets  his  principal  troubles.  The  brilliant  line 
becomes  a  brilliant  point  and  the  tangent  shade  line  a  curve, 
and  to  represent  the  gradation  between  them  by  mechanical 
lines  is  a  difficult  proposition. 
17 


262 


ENGINEERING  DRAWING 


Fig.  442  shows  three  methods  of  shading  a  sphere.  The  bril- 
liant point  and  shade  line  may  be  found  by  revolving  the  pro- 
jecting plane  of  the  ray  passing  through  the  center,  about  its 


FIG.  443. 


FIG.  444. — Shaded  double  curved  surfaces. 

vertical  trace  as  in  Fig.  443,  but  in  practice  these  are  usually 
"guessed  in."  The  first  method  (a)  is  the  commonest.  Con- 
centric circles  are  drawn  from  the  center,  with  varying  pitch, 


NOTES  ON  COMMERCIAL  PRACTICE  263 

and  shaded  on  the  lower  side  by  springing  the  point  of  the  com- 
pass. In  (b)  the  brilliant  point  is  used  as  center.  In  (c),  the 
"wood  cut"  method,  the  taper  on  the  horizontal  lines  is  made 
by  starting  with  the  pen  out  of  perpendicular  and  turning  the 
handle  up  as  the  line  progresses. 

Fig.  444  shows  several  applications  with  double  curved  surfaces 
of  different  kinds. 

Patent  Office  Drawings. 

In  the  application  for  letters  patent  on  an  invention  or  dis- 
covery there  is  required  a  written  description  called  the  specifi- 
cation, and  in  case  of  a  machine,  manufactured  article,  or  device 
for  making  it,  a  drawing,  showing  every  feature  of  the  invention. 
If  it  is  an  improvement,  the  drawing  must  show  the  invention 
separately,  and  in  another  view  a  part  of  the  old  structure  with 
the  invention  attached.  A  high  standard  of  execution,  and  con- 
formity to  the  rules  of  the  Patent  Office  must  be  observed.  A 
pamphlet  called  the  "Rules  of  Practice,"  giving  full  information 
and  rules  governing  patent  office  procedure  in  reference  to  appli- 
cation for  patents  may  be  had  gratuitously  by  addressing  the 
Commissioner  of  Patents,  Washington,  D.  C. 

The  drawings  are  made  on  smooth  white  paper  specified  to  be 
of  a  thickness  equal  to  three-sheet  Bristol-board.  Two-ply 
Reynolds  board  is  the  best  paper  for  the  purpose,  as  prints  may 
be  made  from  it  readily,  and  it  is  preferred  by  the  Office.  The 
sheets  must  be  exactly  10  by  15  inches,  with  a  border  line  one 
inch  from  the  edges.  Sheets  with  border  and  lettering  printed, 
as  Fig.  445,  are  sold  by  the  dealers,  but  are  not  required  to  be  used. 

A  space  of  not  less  than  11/4  inches  inside  of  the  top  border 
must  be  left  blank  for  the  printed  title  added  by  the  Office. 

Drawings  must  be  in  black  ink,  and  drawn  for  a  reproduction 
to  reduced  scale.  As  many  sheets  as  are  necessary  may  be  used. 
In  the  case  of  large  views  any  sheet  may  be  turned  on  its  side 
so  that  the  heading  is  at  the  right  and  the  signatures  at  the  left, 
but  all  views  on  the  same  sheet  must  stand  in  the  same  direction. 

Patent  Office  drawings  are  not  working  drawings.  They  are 
descriptive  and  pictorial  rather  than  structural,  hence  will  have 
no  center  lines,  no  dimension  lines  nor  figured  dimensions,  no 
notes  nor  names  of  views.  The  scale  chosen  should  be  large 
enough  to  show  the  mechanism  without  crowding.  Unessential 


264 


ENGINEERING  DRAWING 


details  or  shapes  need  not  be  represented  with  constructional 
accuracy,  and  parts  need  not  be  drawn  strictly  to  scale.  For 
example,  the  section  of  a  thin  sheet  of  metal  drawn  to  scale 
might  be  a  very,  thin  single  line,  but  it  should  be  drawn  with  a 
double  line,  and  section-lined  between. 

Section  lining  must  not  be  too  fine.  One-twentieth  of  an 
inch  pitch  is  a  good  limit.  Solid  black  should  not  be  used 
excepting  to  represent  insulation  or  rubber. 


3 

T 

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~Y  in  a/  We  f&fefff  <?fifce 

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\ 

ATTORNEY 

T 

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FIG.  445. 

Shade  lines  are  always  added,  except  in  special  cases  where 
they  might  confuse  or  obscure  instead  of  aid  in  the  reading. 

Surface  shading  by  line  shading  is  used  whenever  it  will  add 
to  the  legibility,  but  it  should  not  be  thrown  in  indiscriminately 
or  lavishly  simply  to  please  the  client. 

Gears  and  toothed  wheels  must  have  all  their  teeth  shown, 
and  the  same  is  true  of  chains,  sprockets,  etc.,  but  screw  threads 
may  be  represented  by  the  conventional  symbols.  The  Rules 
of  Practice  gives  a  chart  of  electrical  symbols,  symbols  for  colors, 
etc.,  which  should  be  followed. 

The  drawings  may  be  made  in  orthographic,  axonometric, 


NOTES  ON  COMMERCIAL  PRACTICE  265 

oblique,  or  perspective.  The  pictorial  system  is  used  extensively, 
for  either  all  or  part  of  the  views.  The  examiner  is  of  course  ex- 
pert in  reading  drawings,  but  the  client,  and  sometimes  the  attor- 
ney, .may  not  be,  and  the  drawing  should  be  clear  to  them.  In 
checking  the  drawing  for  completeness  it  should  be  remembered 
that  in  case  of  litigation  it  may  be  an  important  exhibit  in  the 
courts. 

Only  in  rare  cases  is  a  model  of  an  invention  required  by  the 
Office. 

The  views  are  lettered  "Fig.  1,"  "Fig.  2"  etc.,  and  the  parts 
designated  by  reference  numbers  though  which  the  invention  is 
described  in  the  specifications.  One  view,  generally  "Fig.  1," 
is  made  as  a  comprehensive  view  that  may  be  used  in  the  Official 
Gazette  as  an  illustration  to  accompany  the  "claims." 


FIG.  446. 

The  draftsman  usually  signs  the  Hrawing  as  the  first  witness. 
The  inventor  signs  the  drawing  in  the  lower  right-hand  corner. 
In  case  an  attorney  prepares  the  application  and  drawing,  the 
attorney  writes  or  letters  the  name  of  the  inventor,  signing  his 
own  name  underneath  as  his  attorney. 

To  avoid  making  tack  holes  in  the  paper  it  should  be  held  to 
the  board  by  the  heads  of  the  thumb  tacks  only. 

Fig.  446  is  a  clamp  drawing  board  used  by  some  patent  drafts- 
men. 

The  requirements  for  drawings  for  foreign  patents  vary  in 
different  countries,  most  countries  requiring  drawings  and  several 
tracings  of  each  sheet. 

Fig.  447  is  an  example  of  a  patent  office  drawing,  reduced  to 
1/2  size. 

Stretching  Paper  and  Tinting. 

If  a  drawing  is  to  be  tinted  the  paper  should  be  stretched  on 
the  board.  First,  dampen  it  thoroughly  until  limp,  either  with 


266 


ENGINEERING  DRAWING 


WITNESSES: 


Duqizesne  Sprague  INVENTOR. 


FIG.  447. — A  patent  office  drawing. 


NOTES  ON  COMMERCIAL  PRACTICE  267 

a  sponge  or  under  the  faucet,  then  lay  it  on  the  drawing  board 
face  down,  take  up  the  excess  water  from  the  edges  with  a 
blotter,  brush  glue  or  paste  about  one-half  inch  wide  around  the 
edge,  turn  over  and  rub  the  edges  down  on  the  board  until  set, 
and  allow  to  dry  horizontally. 

Drawings  or  maps  on  which  much  work  is  to  be  done,  even 
though  not  to  be  tinted,  may  be  made  advantageously  on 
stretched  paper;  but  Bristol  or  calendered  paper  should  not  be 
stretched. 

Tinting  is  done  with  washes  made  with  moist  water  colors. 
The  drawing  may  be  inked  (with  waterproof  ink)  either  before, 
or  preferably  after  tinting. 

The  drawing  should  be  cleaned  and  the  unnecessary  pencil 
marks  removed  with  a  very  soft  rubber,  the  tint  mixed  in  a 
saucer  and  applied  with  a  camePs-hair  or  sable  brush,  inclining 
the  board  and  flowing  the  color  with  horizontal  strokes,  leading 
the  pool  of  color  down  over  the  surface,  taking  up  the  surplus 
at  the  bottom  by  wiping  the  brush  out  quickly  and  picking  up 
with  it  the  excess  color.  Stir  the  color  each  time  the  brush  is 
dipped  into  the  saucer.  Tints  should  be  made  in  light  washes, 
depth  of  color  being  obtained  if  necessary  by  repeating  the  wash. 
To  get  an  even  color  it  is  well  to  go  over  the  surface  first  with  a 
wash  of  clear  water. 

Diluted  colored  inks  may  be  used  for  washes  instead  of  water 
color. 

Mounting  Tracing  Paper. 

Tracings  are  mounted  for  display,  on  white  mounts,  either  by 
"tipping"  or  "floating."  To  tip  a  drawing  brush  a  narrow 
strip  of  glue  or  paste  around  the  under  edge,  dampen  the  right 
side  of  the  drawing  by  stroking  with  a  sponge  very  slightly 
moistened,  and  stretch  the  paper  gently  with  the  thumbs  on 
opposite  edges,  working  from  the  middle  of  the  sides  toward  the 
corners. 

To  float  a  drawing  make  a  very  thin  paste  and  brush  a  light 
coat  over  the  entire  surface  of  the  mount,  lay  the  tracing  paper 
in  position  and  stretch  into  contact  with  the  board  as  in 
tipping.  If 'air  bubbles  occur  force  them  out  by  rubbing  from 
the  center  of  the  drawing  out,  laying  a  piece  of  clean  paper  over 
the  drawing  to  protect  it. 


268  ENGINEERING  DRAWING 

Mounting  on  Cloth. 

It  is  sometimes  necessary  to  mount  drawings  or  maps  on  cloth. 
The  following  methods  are  used: 

Hot  mounting  is  best  for  both  heavy  and  thin  paper.  For 
heavy  paper,  tack  down  mounting  cloth  with  another  cloth 
under,  put  1/2  pint  library  paste  with  1/2  oz.  water  in  pan 
and  bring  to  boil.  With  broad  brush  paste  back  of  drawing  or 
print  quickly,  working  from  center  out,  turn  over  and  place  on 
cloth.  Have  hot  iron  ready  and  iron  print  from  center  out,  in 
circular  motion,  ironing  fast  until  edges  are  stuck,  then  removing 
tacks  to  release  the  steam  and  ironing  till  dry.  Never  iron  on 
the  back,  as  the  steam  formed  will  cause  blisters. 

Cold  paste 'may  be  used  for  hurry  work,  applying  it  to  the 
cloth  instead  of  the  paper,  and  ironing  as  before. 

For  mounting  thin  paper.  The  print  to  be  mounted  is  rolled, 
face  in,  on  a  large  roller  (a  roll  of  detail  paper  may  be  used), 
hot  paste  applied  starting  at  end,  the  print  rolled  off  on  the 
cloth,  and  followed  up  as  fast  as  unrolled  by  hot  irons.  If  cold 
paste  is  used  apply  it  to  the  cloth.  Never  attempt  to  apply 
cold  paste  on  thin  paper. 

Cold  Mounting.  When  hot  irons  are  not  available,  prints 
may  be  mounted  by  stretching  cloth  tightly  on  table,  applying 
paste,  and  rolling  with  photographic  print  roller,  leaving  the 
cloth  stretched  until  perfectly  dry. 

Methods  of  Copying  Drawings. 

Drawings  are  often  copied  on  opaque  paper  by  laying  the 
drawing  over  the  paper  and  pricking  through  with  a  needle 
point,  turning  the  upper  sheet  back  frequently  and  connecting 
the  points.  Prickers  may  be  purchased,  or  may  be  m,ade  easily 
by  forcing  a  fine  needle  into  a  soft  wood  handle.  They  may  be 
used  to  advantage  also  in  accurate  drawing,  in  transferring 
measurements  from  scale  to  paper. 

Transfer  by  Rubbing. 

This  method  is  used  extensively  by  architects,  and  may  be 
used  to  good  advantage  in  transferring  any  kind  of  sketch  or  de- 
sign to  the  paper  on  which  it  is  to  be  rendered. 

The  original  is  made  on  any  paper,  and  may  be  worked  over, 
changed,  and  marked  up  until  the  design  is  satisfactory.  Lay 


NOTES  ON  COMMERCIAL  PRACTICE  269 

a  piece  of  tracing  paper  over  the  original  and  trace  the  outline 
carefully.  Turn  the  tracing  over  and  retrace  the  outline  just 
as  carefully  on  the  other  side,  using  a  medium  soft  pencil  (perhaps 
H  or  2H)  with  a  sharp  point.  Turn  back  to  first  position  and  tack 
down  smoothly  over  the  paper  on  which  the  drawing  is  to  be 
made,  registering  the  tracing  to  proper  position  by  center  or 
reference  lines  on  both  tracing  and  drawing.  Now  transfer  the 
drawing  by  rubbing  the  tracing  with  the  rounded  edge  of  a 
knife  handle  or  other  instrument  (a  smooth-edged  coin  held 
between  thumb  and  forefinger  and  scraped  back  and  forth  is 
commonly  used),  holding  a  small  piece  of  tracing  cloth  with 
smooth  side  up  between  the  rubbing  instrument  and  the  paper, 
to  protect  the  paper.  Do  not  rub  too  hard,  and  be  sure  that 
neither  the  cloth  nor  paper  move  while  rubbing. 

Very  delicate  drawings  can  be  copied  with  great  accuracy  in 
this  manner. 

If  the  drawing  is  symmetrical  about  any  axis  the  reversed 
tracing  need  not  be  made,  but  the  rubbing  can  be  made  from 
the  first  tracing  by  reversing  it  about  the  axis  of  symmetry. 


P&fffeGtoss 


FIG.  448. — A  transparent  drawing  board. 

Several  rubbings  can  be  made  from  one  tracing,  and  when  the 
same  figure  or  detail  must  be  repeated  several  times  on  a  drawing 
much  time  can  be  saved  by  drawing  it  on  tracing  paper  and 
rubbing  it  in  the  several  positions. 

A  Transparent  Drawing  Board. 

A  successful  device  for  copying  drawings  on  opaque  paper  is 
illustrated  in  Fig.  448.  A  wide  frame  of  white  pine  carrying  a 
piece  of  plate  glass  set  flush  with  the  top,  is  hinged  to  a  base 
lined  with  bright  tin.  A  sliding  bar  carries  two  show-case  lamps, 
whose  light  may  thus  be  concentrated  under  any  part  of  the 


2fO 


ENGINEERING  DRAWING 


drawing.  Ventilation  and  protection  from  overheating  is  provided 
by  the  ground  glass  and  air  space  between  it  and  the  plate  glass. 

The  frame  has  a  piece  of  felt  glued  on  the  bottom  and  may  be 
used  on  the  top  of  any  table  where  connection  with  an  electric 
light  outlet  is  convenient. 

Drawings  even  in  pencil  may  be  copied  readily  on  the  heaviest 
paper  or  Bristol-board  by  the  use  of  this  device. 


FIG.  449.— Pantograph. 

The  Pantograph. 

The  principle  of  the  pantograph,  used  for  reducing  or  enlarging 
drawings  in  any  proportion,  is  well  known.  Its  use  is  often  of 
great  advantage.  It  consists  essentially  of  four  bars,  which  for 
any  setting  must  form  a  parallelogram,  and  have  the  pivot, 


FIG.  450. — Suspended  pantograph. 

tracing  point,  and  marking  point  in  a  straight  line;  and  any 
arrangement  of  four  arms  conforming  to  this  requirement  will 
work  in  true  proportion.  Referring  to  Fig.  449  the  scale  of 
enlargement  is  PM/PT  or  AM/AB.  For  corresponding  reduc- 
tion the  tracing  point  and  marking  point  are  exchanged. 


NOTES  ON  COMMERCIAL  PRACTICE 


2ft 


The  inexpensive  wooden  form  of  Fig.  449  is  sufficiently  accurate 
for  ordinary  outlining.  A  suspended  pantograph  with  metal 
arms,  for  accurate  engineering  work,  is  shown  in  Fig.  450. 

Drawings  may  be  copied  to  reduced  or  enlarged  scale  by  using 
the  proportional  dividers. 

The  well-known  method  of  proportional  squares  is  often  used 
for  reduction  and  enlargement.  The  drawing  to  be  copied  is 
ruled  in  squares  of  convenient  size,  or,  if  it  is  undesirable  to  mark 
on  the  drawing,  a  sheet  of  ruled  tracing  cloth  or  celluloid  is  laid 
over  it,  and  the  copy  made  freehand  on  the  paper,  which  has 
been  ruled  in  corresponding  squares,  larger  or  smaller,  Fig.  451. 


FIG.  451. — Enlargement  by  squares. 

About  Tracings. 

Sometimes  it  is  desired  to  add  an  extra  view,  or  a  title,  to  a 
print  without  putting  it  on  the  tracing.  This  may  be  done  by 
drawing  the  desired  additions  on  another  piece  of  cloth  of  the 
same  size  as  the  original,  and  printing  the  two  tracings  together. 

A  figure  may  be  taken  out  of  a  tracing,  and  another  inserted 
by  making  an  "  inlay, "  laying  the  new  piece  under  the  tracing  and 
cutting  through  both  together  with  a  sharp  knife,  then  fastening 
the  new  piece  in  the  hole  with  collodion. 

Do  not  take  up  a  blot  with  a  blotter,  but  scoop  it  up  with  the 
finger,  leaving  a  smear.  Erase  the  smear  when  dry,  with  a 
pencil  eraser. 


272  ENGINEERING  DRAWING 

To  prevent  smearing  in  cleaning,  titles  if  printed  from  type  on 
tracing  cloth  should  be  printed  in  an  ink  not  affected  by  benzine. 
Local  printers  are  often  unable  to  meet  this  requirement,  but 
there  are  firms  which  make  a  specialty  of  this  kind  of  printing. 

Preserving  Drawings. 

A  drawing,  tracing,  or  blue  print  which  is  to  be  handled  much 
may  be  varnished  with  a  thin  coat  of  white  shellac. 

Prints  made  on  sensitized  cloth  will  withstand  hard  usage. 

A  method  of  imbedding  drawings  in  sheet  celluloid,  making 
them  water-  and  grease-proof,  is  carried  on  by  the  Dodge  Motor 
Map  Co.,  N.  Y.  The  cost  is  about  fifty  cents  a  square  foot. 

Blue  prints  for  shop  use  are  often  mounted  for  preservation 
and  convenience,  by  pasting  on' tar  board  or  heavy  press  board 
and  coating  with  white  shellac  or  Damar  varnish.  A  coat  of 
white  glue  under  the  varnish  will  aid  still  further  in  making  the 
drawings  washable. 

Tracings  to  which  more  or  less  frequent  reference  will  be  made 
should  be  filed  flat  in  shallow  drawers.  Sets  of  drawings  pre- 
served only  for  record  are  often  kept  in  tin  tubes  numbered  and 
filed  systematically.  A  pasteboard  tube  with  screw  cover  is  also 
made  for  this  purpose.  It  is  lighter  than  tin  and  withstands 
fire  and  water  even  better. 

Fireproof  storage  vaults  should  always  be  provided  in  connec- 
tion with  drafting  rooms. 


FIG.  452. 

Miscellaneous  hints. 

A  temporary  adjustment  of  a  T-square  may  be  made  by  put- 
ting a  thumb  tack  in  the  head,  Fig.  452. 

A  homemade  ellipsograph  has  been  made  on  the  principle  of 
the  pin-and-string  method  of  Fig.  90  by  adding  a  clip  to  the 
compass  pen  to  hold  the  string,  which  will  pull  the  leg  in  as  the 
compass,  with  its  center  at  0,  moves  from  B  to  D. 


NOTES  ON  COMMERCIAL  PRACTICE  273 

If  much  ruling  in  red  ink  is  done,  a  pen  for  the  purpose  with 
nickel  plated  or  german  silver  blades  is  advisable. 

A  steel  edge  to  a  drawing  board  is  made  of  an  angle  iron  planed 
straight  and  set  flush  with  the  edge.  With  this  edge  and  a 
steel  T-square  very  accurate  plotting  may  be  done.  These  are 
often  used  in  bridge  offices. 


CHAPTER  XV.  * 
BIBLIOGRAPHY  OF  ALLIED  SUBJECTS. 

The  present  book  has  been  written  as  a  general  treatise  on  the 
language  of  Engineering  Drawing.  The  following  short  classi- 
fied list  of  books  is  given  both  to  supplement  this  book,  whose 
scope  permitted  only  the  mention  or  brief  explanation  of  some 
subjects,  and  as  an  aid  to  those  who  might  desire  the  recommen- 
dation of  a  book  on  some  branch  of  drawing  or  engineering. 

Architectural  Drawing. 

Ware,  Wm.  R.— The  American  Vignola.     2  v.  9  1/2x12  1/2. 
Scranton,  1906. 

Part  I,     The  Five  Orders.     76  pp.,  18  pi.     $2.50. 
Part  II,  Arches  and  Vaults,  Roofs  and  Domes,  Doors 
and  Windows,  Walls  and  Ceilings,  Steps  and 
Staircases.    50  pp.,  19  pi.     $2.50. 

Simple  proportions  for  drawing  the  classic  orders;  and  their 

application  in  composition. 

A  book  every  architectural  draftsman  should  have. 

Martin,    Clarence    A. — Details    of    Building    Construction. 
33  pi.  9  1/2x12  1/2.     $2.00.     Bates  &  Guild,.  1905. 

Suggestive  details  of  domestic  architecture  representing  good 
practice,  principally  in  wood,  as  windows,  cornices,  etc. 

Snyder,  Frank  M. — Building  Details.     Issued  in  parts  of 
10  pi.  each,  16x22.     $2.25  net.     N.  Y.,  1906 

Selections  of  fully  dimensioned  details,  principally  of  large 
buildings,  from  the  drawings  of  various  representative 
architects. 

Descriptive  Geometry. 

Church,    Albert    E. — Elements    of    Descriptive    Geometry. 
286  pp.,  6x8  1/2  rev.  ed.     $2.25  net.     American  Book  Co.,  1911. 

This  book  has  been  a  standard  ever  since  its  original  publica- 
tion in  1864.  The  present  revision  is  by  Geo.  M.  Bartlett. 

Anthony  and  Ashley.— Descriptive  Geometry.     134  pp. ,34 
pi.,  obi.  6x7  1/2.     $2.00.     D.  C.  Heath  &  Co.,  1909. 
A  comprehensive  elementary  treatise. 
274 


BIBLIOGRAPHY  OF  ALLIED  SUBJECTS  275 

MacCord,  C.  W. — Elements  of  Descriptive  Geometry.  248 
pp.,  6x9.  $3.00.  Wiley,  1902. 

Particularly  good  on  auxiliary  planes  and  warped  surfaces. 

Gears  and  Gearing. 

Logue,  Charles  H. — American  Machinist  Gear  Book,  348  pp., 
6x9.  $2.50.  McGraw-Hill,  1910. 

"Simplified  tables  and  formulas  for  designing,  and  practical 
points  in  cutting  all  commercial  types  of  gears." 

Grant,  George  B. — A  Treatise  on  Gear  Wheels,  103  pp., 
6x9.  Phila.  Gear  Works,  1906. 

A  practical  book  on  the  designing  and  cutting  of  gears. 

Anthony,  G.  C. — The  Essentials  of  Gearing.  84  pp.,  15  fold- 
ing pi.,  obi.  6x7  1/2.  $1.50.  D.  C.  Heath  &  Co.,  1897. 

An  elementary  text-book  on  the  drawing  of  tooth  outlines. 

Stutz,  Charles  C.— Formulas  in  Gearing.     6x9,  5th  ed.,  183 
pp.,  $2.00.     Brown  and  Sharpe  Mfg.  Co.,  1907. 
Useful  formulas  for  gear  design. 

Handbooks. 

A  great  many  "pocket  size"  handbooks,  with  tables,  formulas, 
and  information  are  published  for  the  different  branches  of 
the  engineering  profession,  and  draftsmen  keep  the  ones 
pertaining  to  their  particular  line  at  hand  for  ready  reference. 
Attention  is  called,  however,  to  the  danger  of  using  handbook 
formulas  and  figures  without  understanding  the  principles 
upon  which  they  are  based.  "  Handbook  designer"  is  a  term 
of  reproach  applied  not  without  reason  to  one  who  depends 
wholly  upon  these  aids  without  knowing  their  theory  or 
limitations. 

Among  the  best  known  of  these  reference  books  are  the 
following: 

American  Civil  Engineers'  Pocketbook,  Mansfield  Merriman, 
ed.  in  chief.  1380  pp.  $5.00  net.  Wiley,  1911. 

A  new  book  by  a  corps  of  well-known  engineers. 

American  Machinists'  Handbook,  and  Dictionary  of  Shop 
Terms,  by  F.  H.  Colvin  and  Frank  A  Stanley.  513  pp.  $3.00  net. 
McGraw-Hill,  1908. 

"  A  reference  book  on  machine-shop  and  drawing-room  data, 
methods  and  definitions." 

Architects'  and  Builders'  Pocketbook,  F.  E.  Kidder. 
15th  ed.,  1661  pp.  $5.00.  Wiley,  1908. 

The  standard  architects'  reference  book. 


276  ENGINEERING  DRAWING 

Cambria  Steel. — A  Handbook  of  Information  Relating  to 
Structural  Steel  Manufactured  by  the  Cambria  Steel  Co.  468  pp. 
$1.00.  Phila.,  1907. 

A  standard  book  for  structural  steel  designers. 

Carnegie. — Pocket  Companion  containing  Useful  Informa- 
tion and  Tables  appertaining  to  the  Use  of  Steel  as  manufactured 
by  the  Carnegie  Steel  Co.  345  pp.  $2.00.  Pittsburg,  1903. 

Catalogue  of  Bethlehem  Structural  Shapes,  Manufactured 
by  Bethlehem  Steel  Co.    ,72  pp.     Bethlehem,  Pa.,  1909. 
Contains  tables  for  shapes  rolled  by  this  company. 

Civil  Engineers'  Pocketbook,  J.  C.  Trautwine.  19th  ed., 
1257  pp.  $5.00  net.  Trautwine  Co.,  Phila.,  1909. 

The  best  known  reference  book  for  civil  engineers. 

Electrical  Engineers'  Pocketbook.  H.  A.  Foster,  ed., 
1599  pp.  $5.00.  D.  Van  Nostrand,  N.  Y.,  1908. 

"A  handbook  of  useful  data  for  electricians  and  electrical 
engineers." 

Handbook  of  Cost  Data.  H.  P.  Gillette.  1841  pp.  $5.00. 
Myron  C.  Clark,  Chicago,  1910. 

For  civil  engineers  and  contractors. 

Mechanical  Engineers'  Pocketbook.  Wm.  Kent.  8th  ed., 
1461  pp.  $5.00  net.  Wiley,  1910. 

"  A  reference  book  of  rules,  tables,  data,  and  formulae,  for  the 
use  of  engineers,  mechanics,  and  students."  Universally 
known  by  mechanical  engineers. 

Mechanical  Engineers'  Reference  Book.  H.  H.  Suplee. 
3rd  ed.,  922  pp.  $5.00  net.  J.  B.  Lippincott,  Phila.,  1907. 

"  A  handbook  of  tables,  formulas,  and  methods  for  engineers, 
students,  and  draftsmen." 

Standard  Handbook  for  Electrical  Engineers.  3rd  ed., 
1500  pp.  $4.00  net.  McGraw-Hill,  1910. 

Contains  a  more  complete  theoretical  treatment  than  Foster. 
Of  particular  value  to  students. 

Machinery  Data  Sheets,  6x9  "Machinery"  N.  Y. 

A  series  of  data  sheets  for  designers,  published  as  supplements 
to  the  periodical.  Back  numbers  cut  and  bound  may  be 
purchased. 

Lettering. 

French  (Thos.    E.)   and  Meiklejohn,   (R).— The   Essentials 
of  Lettering.     3d  ed.,  76  pp.,  6x9.     $1.00.     McGraw-Hill,  1911. 
"  A  manual  for  students  and  designers." 


BIBLIOGRAPHY  OF  ALLIED  SUBJECTS  277 

Reinhardt,  Chas.  W. — Lettering  for  Draftsmen,  Engineers, 
and  Students.  23  pp.,  8  pi.,  8x11.  $1.00  net.  D.  Van  Nostrand, 
1895. 

A  complete  analysis  of  the  single-stroke  "Reinhardt"  letter. 

Machine  Drawing  and  Design. 

A  great  many  text-books  and  reference  books  have  been 
written  on  machine  drawing  and  designing.  A  few  only  are 
noted  here. 

Unwin,  William  C. — Elements  of  Machine  Design. 

Part    I,  General  principles,  fastenings  and  transmission 
machinery,    new  ed.,    531  pp.,   5  1/2x8  1/2. 
$2.50.     Longmans,  Green  &  Co.,  1909. 
Part  II,  Engine  details  431  pp.,  5x7.    $2.00.    Longmans, 

Green  &  Co.,  1902. 

A  standard  English  text-book  widely  used  in  this  country. 
Spooner,    Henry    J. — Machine    Design,    Construction,    and 
Drawing.     691  pp.,  5  1/2x8  1/2.     $3.50  net.     Longmans,  Green 
&  Co.,  1910. 

Another  English  text-book  conforming  to  .modern  English 
engineering  practice. 

Cathcart,  W.  E.  L. — Machine  Design. 

Part   I,  Fastenings,  6x9  1/2,  291  pp.     $3.00  net.     Van 
Nostrand,  1903. 

A  good  reference  book  giving  modern  American  data  from 
best  practice.  » 

Kimball  and  Barr. — Elements  of  Machine  Design.  446  pp., 
6x9.  $3.00.-  Wiley,  1909. 

A  text-book  with  discussion  of  the  fundamental  principles  of 
design. 

Reid  (John  S.)  and  Reid  (David). — A  Text-book  of  Mechani- 
cal drawing  and  Elementary  Machine  Design.  439  pp.,  6x9. 
$3.00.  Wiley,  1910. 

Contains  an  interesting  summary  of  an  investigation  into 
present  practice  in  drafting-room  conventions  and  methods. 

Jepson,  George. — Cams  and  the  Principles  of  their  Construc- 
tion. 59  pp.,  6x9.  $1.50  net.  Van  Nostrand,  1905. 

A  short  discussion  of  various  forms  of  cams  and  the  methods 
of  drawing  them. 

Mechanism. 

Robinson,  S.  W. — Principles  of  Mechanism.     A  Treatise  on 
the  Modification  of  Motion  by  means  of  the  Elementary  Combina- 
18 


278  ENGINEERING  DRAWING 

tions  of  Mechanism,  or  of  the  Parts  of  Machines.     309  pp.,  6x9. 

$3.00.     Wiley,  1900. 

The  authority  on  non-circular  gearing.     Treatment  mainly 
by  graphics  instead  of  analysis. 

Barr,  John  H. — Kinematics  of  Machinery.    2nd  ed.,  264  pp., 

6x9.     $2.50.     Wiley,  1911. 

"  A  brief  treatise  on  constrained  motion  of  machine  elements." 
(Revised  by  Edgar  H.  Wood.) 

Dunkerley,  S.— Mechanism.     2nd  ed.,  448  pp.,  6x9.     $3.00. 

Longmans,  Green  &  Co.,  1907. 

A  modern  text-book  on  the  kinematics  of  machines,  used  in 
English  colleges. 

Perspective. 

Ware,  Wm.  R. — Modern  Perspective,  a  Treatise  upon  the 
Principles  and  Practice  of  Plane  and  Cylindrical  Perspective, 
6th  ed.,  336  pp.,  5x7  1/2  and  atlas  of  plates.  $4.00.  MacMillan, 
1900. 

An  exhaustive  work. 

Longfellow,  Wm.  P.  P. — Applied  Perspective  for  Architects 
and  Painters.  8x11,  95  pp.,  33  pi.  $2.50  net.  Houghton, 
Mifflin  &  Co.,  1901. 

A  practical  book  on  architectural  perspective. 

Fuchs,  Otto. — Handbook  on  Linear  Perspective,  Shadows 
and  Reflections.  8x10,  34  pp.,  13  folding  pi.  $1.00  Ginn  &  Co., 
1902. 

An  elementary  presentation  in  problem  form,  for  artists  and 
architects. 

Wilson,  Victor  T.— Freehand  Perspective.  5  1/2x9,  257  pp. 
$2.50.  Wiley,  1900. 

A  thorough  discussion  of  the  principles  and  their  application 
in  freehand  sketching. 

Mathewson,  Frank  E. — Perspective  Sketching  from  Work- 
ing Drawings.  5x8,  77  pp.  $1.00.  The  Taylor-Holden  Co., 
1908. 

A  good  elementary  book  on  freehand  perspective. 
Frederick,  Frank  Forrest.— Simplified  Mechanical  Perspec- 
tive, 54  pp.,  7x10,    75  cents.     The  Manual  Arts  Press,  1909. 

An  elementary  explanation  of  linear  perspective. 
Rendering. 

Maginnis,  Charles  D. — Pen  Drawing.  An  Illustrated  Treat- 
ise. 130  pp.,  5x7  1/2.  $1.00  net.  Bates  &  Guild,  1904. 

By  a  well-known  architect.     Should  be  in  the  library  of  every 
architectural  draftsman. 


BIBLIOGRAPHY  OF  ALLIED  SUBJECTS  279 

Frederick,  Frank  F.— The  Wash  Method  of  Handling  Water 
Color.     16  pp.,  7x10.     50  cents.     Manual  Arts  Press,  1908. 
A  helpful  little  guide  in  the  use  of  water  color. 

Shades  and  Shadows. 

McGoodwin,    Henry. — Architectural    Shades    and    Shadows. 
118  pp.,  9  1/2x12.     $3.00.     Bates  &  Guild,  1904. 

The  principles  of  casting  shadows,  and  their  application  on 
architectural  forms. 

Sheet  Metal. 

Kittredge,  Geo.  W.— The  New  Metal  Worker  Pattern  Book. 
429  pp.,  9x11  1/2.     $5.00.     David  Williams,  N.  Y.,  1911. 

An  exhaustive  treatise  on  the  principles  and  practice  of  pattern 
cutting  as  applied  to  sheet  metal  work. 

Stereotomy. 

French  (A.  W.)  and  Ives  (H.  C.).— Stereotomy.     119  pp., 
21  folding  pi.,  6x9.     $2.50.     Wiley,  1902. 

Contains  practical  examples  of  the  application  of  stone  cut- 
ting in  architectural  and  engineering  structures. 

Warren,   S.   E. — Stereotomy,   Problems  in  Stone   Cutting. 

126  pp.,  10  folding  pi.,  6x9.     $2.50.'    Wiley,  1893. 
For  civil  engineering  students. 

Structural  Drawing. 

Morris,  Clyde  T. — Designing  and  Detailing  of  Simple  Steel 
Structures.     201  pp.,  6x9.     $2.75.     Eng.  News,  N.  Y.,  1909. 

A  clear  and  concise  text  for  both  students  and  practical  men. 

Surveying. 

Johnston,  J.    B. — The  theory  and  Practice  of  Surveying. 
17th  ed.     Rewritten  by  L.  S.  Smith,  921  pp.,  5  1/2x8.     $3.50  net. 

Wiley,  1911. 

A  standard  work  on  surveying. 

Breed  and  Hosmer. — The  Principles  and  Practice  of  Sur- 
veying.    2  v.,  6x9.     Wiley,  1908. 

V.     I,  546  pp.,  Plane  and  Topographic  Surveying.     $3.00. 
V.  II,  432  pp.,  Higher  Surveying.     $2.50. 

Another  standard  work  with  very  full  discussion  of  drafting- 
room  practice. 

Tracy,   John  C.— Plane  Surveying.     792   pp.,  4x7.     $3.00. 

Wiley,    1907. 

A  text-book  and  manual  in  convenient  handbook  form.     A 
thorough  and  practical  book  on  plane  surveying. 


280  ENGINEERING  DRAWING 

Technic  and  Standards. 

Follows,  Geo.  H. — Universal  Dictionary  of  Mechanical 
Drawing,  60  pp.,  8x11.  $1.00.  Eng.  News,  N.  Y.,  1906. 

A  book  of  proposed  standards  and  conventions  to  introduce 

better  uniformity. 

Reinhardt,  Charles  W. — The  Technic  of  Mechanical  Draft- 
ing. 3rd  ed.,  42  pp.,  11  pi.  $1.00.  Eng.  News,  N.  Y.,  1909. 

A    guide    to    good    technic,    particularly    for    drawing   for 
reproduction,  with  excellent  examples  of  work. 

Topographical  Drawing. 

Reed,  Lieut.  H.  A. — Topographical  Drawing  and  Sketching, 
Including  Applications  of  Photography.  2  v.  in  one,  140  +  88 
pp.,  26  folding  pi.,  9x12.  $5.00.  Wiley,  1890. 

An  exhaustive  text  and  reference  book  on  the  subject. 

Daniels,  Frank  T. — A  Text-book  of  Topographical  Drawing. 
144  pp.,  6x7  1/2.  $1.50.  D.  C.  Heath  &  Co.,  1908. 

A  well  arranged  book  on  ink  and  color  topography,   with 
practical  problems. 

Wilson,  H.  M. — Topographic  Surveying.  3rd  ed.,  910  pp., 
6x9.  $3.50.  Wiley,  1908. 

A   complete  work   on   topographic   surveying,    containing   a 
chapter  on  topographical  drawing. 


INDEX 


INDEX 


A. 

Acme  threads,  159 
Adjustable  head  T-square,  10 
Air-brush,  255 

A.  L.  A.  M.  standard  bolts,  165 
Alignment,  profile,  246 

test  for,  7 

Allen  set  screw,  167 
Alphabet  of  lines,  39 
Alteneder,  Theo.,  5 

bottle  holder,  22 
Arc,  to  rectify,  49 

through  three  points,  48 

tangent  to  two  lines,  48 
Architectural  drawing,  214 
books  on,  274 

symbols,  220 
Architect's  scale,  11 
Arkansas  oil  stone,  257 
Artist,  1,  66 
Assembly  drawing,  147 
Auxiliary  views,  74,  75,  76 

problems,  91 
Axes,  of  revolution,  82,  83 

isometric,  124 

reversed,  127 
Axonometric  projection,  133 

sketching,  207 

B. 

Babbitt  metal,  174 
Beam  compass,  18 
Bill  of  material,  152,  181 

examples  of,  154 
Black  prints,  251 
Blue  line  prints,  251 
Blue  print  paper,  250 

frame,  250 

from  typewritten  sheet,  251 

machines,  251 

mounting,  272 

to  change,  251 


Blue  printing,  249 
Bolts,  162 

A.  L.  A.  M.  standard,  165 

table  of  U.  S.  standard,  163 
Books,  274 
Border  pen,  17 
Bottle  holders,  22 
Bow  instruments,  8 

use  of,  33 

Breaks,  conventional,  176 
Briggs  pipe  thread,  168 
Bristol  board,  15,  270 

patent  office,  263 
Broken  section,  79 
Brown  prints,  251 
Buttress  thread,  159 

C. 

Cabinet  projection,  133 
Cap  screws,  165 
Castellated  nut,  165 
Cautions,  46 
Cavalier  projection,  129 
Checking,  178 
Chinese  white,  248,  255 
Circle,  involute  of,  56 

isometric,  125,  126 

oblique,  132 

to  draw,  32 

to  shade,  86 
Circular  arc   through  three  points, 

48 

City  plat,  254 

Clinographic  projection,  134 
Colored  inks,  248,  267 
Commercial  sizes,  177 
Compass,  7 

beam,  18 

use  of,  31 
Cones,  development  of,  105 

development  of  oblique,  108 

intersection  of,  114 


283 


284 


INDEX 


Cones,    intersection    with   cylinder, 
112 

shading,  260 
Conic  sections,  50 
Conical  helix,  157 
Conjugate  axes,  52 
Contour  map,  230,  237 
Contour  pen,  17 
Contours,  235 
Conventional  symbols,  see  Symbols 

threads,  159,  160 
Copying  drawings, 

by  pantograph,  270 

by  pricking,  268 

by  proportional  squares,  271 

by  rubbing,  268 

by  tracing,  248 

by  transparent  drawing  board, 

269 
Cross-hatching,  80 

conventional,  175 

instruments  for,  19 

on  patent  drawings,  264 
Cross-section  paper,  206 
Crystallography,  134,  135 
Culture,  symbols  for,  240 
Curve,  ogee,  48 

to  ink  with  circle  arcs,  54 
Curve  pen,  17 
Curves,  14 

use  of,  41 
Cycloid,  55 
Cylinders,  development  of,  102 

intersection  of,  111 

intersection  with  cones,  112 

shading,  260 

D. 

Design  drawing,  147 
Details,  architectural,  226 
Detail  drawing,  147 

papers,  16 

pen,  8 
Descriptive  geometry,  66 

books  on,  274 
Development,  101 

cone,  101 

cylinder,  102 


Development,  elbow,  103 

hexagonal  prism,  102 

oblique  cone,  108 

octagonal  dome,  105 

pyramid,  105 

sphere,  107 

truncated  cone,  105 
Dimensions,  150 

architectural,  226 

of  threads,  162 

on  sketches,  204 

on  structural  drawings,  180 

problems  for,  185 
Dimetric  projection,  133 
Display  drawings,  215 

maps,  232 
Dividers,  7 

hairspring,  7 

plain,  7 

proportional,  17 

use  of,  27 
Dotted  section,  80 
Dotting  pen,  21 
Double  curved  surfaces,  100 

development  of,  107 

shading,  262 
Drafting  machine,  20 
Drawing  boards,  9 

patent  office,  265 

steel  edge  for,  273 

transparent,  269 
Drawing  from  description,  problems, 

98 
Drawing  paper,  15 

pencils,  13 
Drop  pen,  19,  180 
Duplication,  248 

E. 

Elbow,  development  of,  103 
Electrical  symbols,  176 

for  wiring,  221 
Elevations,  223 
Ellipse,  50 

approximate,  four  centers,   53, 

54 

eight  centers,  53 
conjugate  axes,  52 


INDEX 


285 


Ellipse,  parallelogram  method,  52 
pin  and  string  method,  52 
trammel  method,  51 

Ellipsograph,  51 

Engineers'  scale,  11,  35 

English  T-square,  10 

Epicycloid,  55 

Erasing  shields,  22 

Exercises,    in    orthographic    projec- 
tion, 73 
in  reading,  144 
in  sketching,  213 
in  use  of  instruments,  42 

F. 

Farm  survey,  230 

Fastenings,  156 

Faulty  lines,  38 

Finish  mark,  152 

First  angle  projection,  70 

Five-centered  arch,  53 

Flat  scales,  12 

Flexible  curves,  15 

Floating,  267 

Floor  plans,  222,  223 

Form  in  drawing,  23 

Forms  of  threads,  158 

Freehand  drawing,  2,  201,  214 

French  curve,  14,  41 

G. 

Gardener's  ellipse,  52 
Gears,  173 

books  on,  275 
Geometry,  applied,  47 

descriptive,  66 
Good  form,  23 

Gore  method  of  development,  107 
Grouping,  148 

H. 

Hachuring,  237 
Half  section,  79 

isometric,  129 

problems,  95 
Half-tones,  255 
Handbooks,  275 
Headless  set  screw,  167 


Heart  cam,  57 
Helical  spring,  158 
Helix,  157 
Hill  shading,  236 
Hook-spring  bows,  8 
Hot  mounting,  268 
Hyperbola,  50,  55 
Hypocycloid,  55 

I. 

Ink,  drawing,  13 

for  printing  on  cloth,  272 

frozen,  46 

stick,  13 

to  remove,  249,  271 
Inking,  35,  36,  37,  248 

order  of,  149 
Instruments,  list  of,  4,  5 

patterns  of,  7 

selection  of,  4 

spring  bow,  8 

use  of,  23 

Intersection  of  surfaces,  111 
Involute,  56 
Irregular  curves,  14,  41 
Isometric  details,  226 

drawing,  122 

K. 

Kelsey  triangle,  22 
Knuckle  thread,  159 

L. 

Lengthening  bar,  33 
Left-handed  person,  25 
Lettering,  58 

architectural,  227 

books  on,  276 

on  maps,  242 

on  working  drawings,  153 

pen,  to  make,  258 

pens,  13,  17,  59 

single  stroke,  58 

triangle,  10 
Line  shading,  88,  259 
Lines,  alphabet  of,  39 

faulty,  38 

tangent,  38 


286 


INDEX 


Lines,  to  divide  by  trial,  28 

to  divide  geometrically,  47 

to  draw  parallel,  30 

to  draw  perpendicular,  30 

Lithography,  256 

Logarithmic  spiral  curves,  14 

Lock  nuts,  164 

M. 

Machine  drawing,  145 
books  on,  277 

screws,  167 
Maltese  cross,  44 
Mapping  pens,  14 
Maps,  classification  of,  229 

reproduction  of,  256 
Mechanical  drawing,  2 
Mechanigraph,  252 
Mechanism,  books  on,  277 
Millwork  details,  226 
Mosaic,  215 
Mounting  on  cloth,  268 

tracing  paper,  267 

N. 

National   Electrical   Contractors 
Association  Symbols,  221 
Negative  prints,  251 
Notes  and  specifications,  152,  227 
Non-isometric  lines,  124 

O. 

Oblique  projection,  129 

sketching  in,  207 
Octagon,  to  inscribe  in  square,  48 
Octagonal    dome,    development    of, 

105 

"Official  Gazette,"  265 
Offset  construction,  125,  131 

measuring,  205 
Ogee  curve,  48 
Old  Roman  letters,  228 
Order  of  penciling,  148 
Order  of  inking,  149 
Orthographic    projection,    66,    122, 
145 


P. 


Pantograph,  270 


Paper,  bond,  248 

Bristol  board,  15 

detail,  16 

drawing,  15 

profile,  245 

to  mount,  268 

to  stretch,  265 

tracing,  220,  248 

Whatman's,  15 
Parabola,  50,  54 
Patent  office  drawing,  263 

example  of,  265 
Patterns,  100 
Payzant  pen,  18 
Pencil,  24 

for  sketching,  202 

to  sharpen,  24 

compass,  32 

eraser,  15 

pointer,  13 

Penciling,  order  of,  148 
Pencils,  13 
Pens,  border,  17 

curve,  17 

dotting,  21 

drop  or  rivet,  19 

double,  16 

for  lettering,  13,  59 

Payzant,  18 

railroad,  17 

ruling,  7 

to  sharpen,  257 
use  of,  36 

Shepard,  18 

Swede,  8 
Perspective,  65,  122 

angular,  212  p 

books  on,  278 

parallel,  210 

rendering,  215 

sketching  in,  207 
Photo-mechanical  processes,  252 
Pipe,  dimensions  of,  169 

fittings,  170 

threads,  168 
Pivot  joint,  5,  6 
Plans,  architectural,  220 
Plate  girder,  182 


INDEX 


287 


Plats,  230 

city,  234 

subdivisions,  231 
Poch6  rendering,  215 
Polygon,  to  transfer,  48 
Potassium  bichromate,  251 
Preparation  for  drawing,  24 
Prism,  development  of,  102 
Problems, 

Assembly  and  detail  drawings, 
195 

Auxiliary  projections,  91 

Bolts,  screws  and  pipes,  181 

Cabinet  projection,  142 

Checking,  197 

Development  of  cones,  117 
cylinders,  116 
prisms,  115 
pyramids,  116 

Dimensioning,  185 

Drawing  from  description,  98 

Drawing  from  sketches,  186 

Half  sections,  95 

Intersection  of  cylinders,  118 
cylinder  and  cone,  119 
prisms,  118 

surfaces  and  planes,  121 
surfaces  and  planes,  121 
two  cones,  121 

Isometric  drawing,  137 

Isometric  sections,  138 

Machine  parts,  187 

Miscellaneous,  197 

Oblique  drawing,  139 

Orthographic  projection,  88 

Sectional  views,  93 

Triangulation,  117 

True  length  of  lines,  97 

Use  of  instruments,  42 
Profiles,  245,  246 
Projection,  axonometric,  133 

cabinet,  133 

clinographic,  134 

dimetric,  133 

first  angle,  70 

isometric,  123 

oblique,  129 

orthographic,  66 


Projection,  sectional,  77 

Protractor,  19 

Pyramid,  development  of,  105 

R. 

Railroad  pen,  17 
Record  strip,  153 
Red  ink,  248,  273 
Reducing  glass,  254 
Reinhardt  letters,  63,  228,  242 
Relief,  236 

symbols  for,  240 
Rendering,  215 
Reproduction,  252 
Reversed  axes,  127 
Revolution,  81 

problems,  96 

to  isometric  position,  122 
Revolved  section,  79,  226 
Reynolds  Bristol  board,  15,  263 
Rib,  section  through,  146 
Rivet  pen,  19 
Rivets,  180 

Rondinella  triangle,  22 
Roof  truss,  183 
Rubbing  a  copy,  268 
Ruling  pens,  7 

to  sharpen,  257 

use  of,  35,  36,  37 
Ruled  surfaces,  100 
Rules  for  dimensioning,  150,  151 

for  oblique  drawing,  130 

S. 

Scales,  architects',  11 

engineers',  11 

flat,  12 

triangular,  12 

use  of,  34 
Screws,  machine,  167 

various,  168 
Screw  threads,  157 
Section,  architectural,  225 

isometric,  129 

through  rib,  146 

wall,  224 
Sectional  views,  77,  78,  79,  80 

problems,  93 


288 


INDEX 


Section  liners,  19 

lining,  80 

conventional,  175 
on  patent  drawings,  264 
Set  screws,  167 
Sewer  map,  234 

Shades  and  shadows,  book  on,  279 
Shade  lines,  86 

isometric,  129 

on  maps,  232 

on  patent  drawings,  264 
Sheet  metal,  101 

book  on,  279 
Shepard  pen,  18 
Single  curved  surfaces,  100 

to  shade,  260 
Single  stroke  inclined  letters,  61 

vertical  letters,  59 
Sketching,  201 

architectural,  215 

by  pictorial  methods,  206 

from  memory,  203 

in  orthographic,  203 

on  cross-section  paper,  206 
Specifications,  152,  214,  227 
Spiral  of  Archimedes,  57 
Sphere,  development  of,  107 

in  isometric  drawing,  127 

shading,  262 
Spring  bow  instruments,  8 

use  of,  33 
Stages,  in  drawing  bolt  head,  164 

in  drawing  threads,  160 

in  inking,  149 

in  penciling,  148 
Stair  details,  226 
Stereotomy,  books  on,  279 
Stick  ink,  13 
Structural  drawing,  179,  180 

book  on,  279 

examples  of,  182,  183 
Street  paving  intersection,  43 
Studs,  166 

Style  in  drawing,  148 
Subdivision  maps,  231 
Surfaces,  classification  of,  100 
Surveying,  books  on,  279 
Swastika,  43 


Swede  pen,  8 

Swivel  pen,  17 

Symbols,  for  materials,  175 

architectural,  220 

culture,  240 

electrical,  176,  221 

oil  and  gas,  242 

relief,  240 

riveting,  180 

topographic,  239 

vegetation,  242 

water  features,  241 

wiring,  221 

T. 

T-square,  9,  10,  11 

use  of,  25 
Table,  A.  L.  A.  M.,  bolts,  165 

cap  screws,  166 

cast  iron  pipe  fittings,  170 

malleable  pipe  fittings,  171 

standard  pipe  dimensions,  169 

U.  S.  standard  bolts,  163 
Tapped  holes,  160 
Technic  and  standards,   books  on, 

280 

Technical  sketching,  2,  201 
Test  for  alignment,  7 
Test  for  triangles,  11 
Threads,  forms  of,  158 
Thumb  tacks,  12 
Tinting,  267 
Tipping,  267 
Titles,  64 

architectural,  228 

on  maps,  242 

on  working  drawings,  153,    155 

printed,  155,  156 
Tit  quill  pen,  14 
Tongue  joint,  5 
Topographic  symbols,  239 
Topographical  drawing,  235 

books  on,  280 
Tracing  cloth,  248 
Tracing  paper,  220,  269 

to  mount,  267 
Tracings,  249,  271 

filing,  272 


INDEX 


289 


Transfer  by  rubbing,  268 
Transition  pieces,  209 
Transparentizing,  251 
Trial  method  of  dividing  a  line,  28 
Triangles,  10 

special  forms,  21 

test  for,  11 

use  of,  29 

Triangular  scales,  12 
Triangulation,  107 
True  length  of  lines,  84,  85 

problems,  97 

True  size  of  inclined  surfaces,  74 
Turned  section,  79,  226 

U. 

Universal  drafting  machine,  20 
U.  S.  Geological  survey  maps,  245 
U.  S.  N.  Conventional  symbols,  175 

V. 

Van  Dyke  paper,  251 
Vanishing  points,  209 

of  oblique  lines,  213 
Vegetation  symbols,  242 


Vertical  drawing  board,  21 
Violation  of  rules,  145 

W. 

Warped  surfaces,  100 
Wash  drawings,  215 

reproduction  of,  255 
Water  color  tinting,  267 
Water  features,  symbols  for,  241 
Water  lining,  238 
Wax  process,  255 
Wedge  point  pencil,  24 
Whatman  paper,  15 
Whitworth  thread,  159 
Wiring  symbols,  221 
Working  drawings,  145 

architectural,  220 

classes  of,  147 
Worm  thread,  159 

Z. 

Zange  triangle,  22 
Zinc  etching,  252 

cost  of,  255 
Zone  method  of 'development,  107 


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